Son (15m) stealing bedwetting pull-ups from sister (11f)

A couple months ago, my daughter told me (40f) that she felt like her drynites (bedwetting pull-ups) had been going missing from the pack. (For context, she wears them every night due to bedwetting issues). We discussed it but i didn't think too much of it, but she kept bringing it up. Apparently, after she started to notice, she started counting them. And she's completely convinced that they are going missing. She says they go missing every now and then rather than ever day or something (like one or two times a week) but it's sometimes multiple each time.
I really wasn't sure what to think. In our house, it's really just my husband and i, and our two children. I really don't know what anybody other than my daughter would do with bedwetting pullups.
My son used to have bedwetting issues and wore similar protection until he was about 12-13 when it seemed to have gone away.

It definitely sounds like a confusing and stressful situation, and I can understand why your daughter is worried. If she’s consistently counting the DryNites and noticing they’re missing, it’s worth taking her concerns seriously. Sometimes kids pick up on things we don’t notice.
Since it’s only your household members with access, it might be helpful to have a calm, private conversation with each person — not accusing anyone, just checking in. There could be an innocent explanation, like someone moving them or using the wrong pack by mistake. But if not, keeping the pull-ups in a place only you and your daughter can access for a while might help you figure out whether they’re still going missing.
Most importantly, reassure your daughter that you believe her and that you’re working on understanding what’s happening. Bedwetting can already feel embarrassing for kids, so knowing you’re on her side will mean a lot.
Hopefully you can get to the bottom of it soon.