"What have I forgotten?"

Madame, you have forgotten that "disabled" seats are for the physically restricted, and certainly not lively wee dogs who should be on the bus floor NOT the seats, despite your attempt to avoid 
criticism by providing a carry on seat cover.
I kept stum as you looked awfully grumpy and, I suspect, ready for an argument. 
I like dogs but not on public transport seating.  ( Or on golf courses. )