Why would a total stranger come up to you, point to the ground and ask what are these?

I just had a very weird encounter at my grocery store. I always mind my own business when I shop but usually I don’t mind if people come up to me, which they sometimes do.
This grown woman, appeared to be in her early or late twenties, came up to me and asked, ” Maam? What are these?” She then pointed to the ground and ran off laughing.
I don’t know if she was making fun of me, what I was wearing. I try not to let things bother me, but I was bothered by this. It had me a little flustered at checkout.
I didn’t see or talk to her before this incident, I have no idea who she is. She never approached me again after but I did see her a few more times in the store.

Why would a grown person do something like that? I’m genuinely confused about this. Does anyone else experience people like this?