I took my 5-year-old to the wrong birthday party. It taught me a lesson about the grace of strangers.

• I was delighted when my shy kindergartener was invited to one of his classmates' birthday parties.
• Even though I didn't recognize the birthday boy or any other parents, I thought everything was fine.
• The people were friendly, and we had fun. A week later, I discovered we'd attended the wrong party.

My son, Bobby, had always been a shy person. When he started kindergarten, I was hoping he'd make a lot more friends.

I was delighted when I saw an Evite in my inbox from a mom inviting him to a classmate's 6th birthday party. The little boy's name was Nathan.

The event took place at a retro slot-car raceway, where you raced tiny, electric-powered replicas of full-size cars on narrow tracks with "grooves," known as "slots."

Neither of us had been to one before, and we were excited to accept the invitation. I was also looking forward to finally meeting the other parents.

I didn't buy a physical gift

I didn't know anyone, partly because Bobby attended a school in a different suburb, about five miles from ours.

He took the bus, so my husband and I never did pick up or drop off. We worked in the city, so there was no waiting at the school gate and chatting with fellow moms and dads.

Nathan's mother asked people to give half the money we'd have spent on gifts to an animal shelter. She'd use the other half to buy something big that he really wanted.

I ignored red flags

I was relieved that I didn't have to go out of my way to purchase a present, so I donated $20 online.

As a result, Bobby and I arrived, empty-handed, at the slot-car venue at 11 am on a rainy Sunday morning. The hostess greeted us at the door.

"Is that Nathan?" I asked, pointing to the child I assumed was her son. The boy had a giant rosette on his sweater. "You mean, Oliver," she replied. It was the first red flag that I ignored.

My son had a lot of fun

I've always been forgetful and apologized profusely. Bobby and I sat down by the racetrack and grabbed his remote control. A dad showed us how to work the cars.

Time went by, and Bobby had a lot of fun. He didn't interact much with the other children, and they didn't interact much with him either. I thought nothing of it because he was often withdrawn in busy settings.

I introduced myself to many of the parents. They talked animatedly in groups and clearly knew each other well. Still, they included me by asking me how Bobby liked the teacher.

"Oh yes, he loves her," I told one of the moms, mentioning the teacher's name. She looked puzzled. It was another red flag, but I didn't see it waving right in front of my face.

I spotted a large pile of presents on a table nearby. Wasn't it odd, I thought, that so many guests bought gifts when Oliver's mom had wanted us to make donations instead? Still, the penny didn't drop.

It was time to cut the birthday cake. I helped hand out the slices. I wanted to leave a good impression. One mom said how nice it was of me. I joked that I was expecting a tip. She laughed politely.

Something was off

We left 15 minutes later. "Did you have a good time?" I asked Bobby. He nodded,

Fast forward a week, and I looked through my email and clicked on the Evite from Nathan's mom. I intended to write down her number and see if her son would be interested in a playdate.

"Come to Nathan's 6th birthday celebration," the invitation said. I thought it was Oliver's party. Something was off. I looked at the date. Nathan's slot-car racing took place at 11 am the previous Saturday, not 11 am the previous Sunday. We missed his party by 24 hours.

Worse, we'd shown up at the wrong party. Most of the kids were much bigger than Bobby. Now I knew why.

We had crashed a party

I recalled the moment when Oliver cut his cake. I was fairly certain there were more than six candles on top.

No wonder there were so many presents on that table. No wonder the woman looked at me strangely when I mentioned the teacher's name.

I cringed. What on earth had Oliver's mom thought of me? I was the bonkers party crasher who showed up uninvited with their kid. I didn't even bring a gift. What if the other parents gossiped about me and sniggered behind my back? It was mortifying.

My negative reaction shifted

After I called Nathan's mom to apologize for missing his party, I took a breath and reflected on what had happened. It was actually quite amusing. My negative reaction shifted. Bobby thoroughly enjoyed himself, which was a promising outcome for someone so shy.

The hostess might have wondered who the heck I was, but she was too considerate to ask and embarrass me in front of people.

Everyone at the party had been warm, kind, and full of goodwill. It didn't matter who I was. They welcomed me with open arms. Those strangers taught me a lesson in grace.