Bashir ended up helping several patrons with cart return based injuries and forgot to return his in the process.
He also invented a cart injury vaccine while helping, but it was shuffled into obscurity by section 31 who had several cart injury assassinations planned.
Bashir has no idea how carts end up back at the cart return, and between O’Brien and Garak he isn’t likely to learn.
Bashir ended up helping several patrons with cart return based injuries and forgot to return his in the process.
He also invented a cart injury vaccine while helping, but it was shuffled into obscurity by section 31 who had several cart injury assassinations planned.