Prams and trolleys improperly parked are a total menace! If you can't keep them out of peoples way, then expect someone to move them!!
I do so frequently, and as far as I'm concerned, if you can't keep your stuff together then tough tittie, someones going to do it for you.
I do imagine the Mum in the room was feeling crap for any number of reasons, but oh well, we all have crap days...
Nothing wrong whatsoever with what you did Tamtam.