Sounds like a great plan Bee
Love the thought if the mice tipping the trap over n then having a feast. Did they watch you put it out, fill it with food, then when ur back was turned, they sent in a mouse commando unit to turn it on its side and get the goodies? Kinda like James Bond in mice terms?!
Seriously, i know they are not nice. Maybe you could wedge the trap between something on either side so it doesn't tip over. Something heavy either side so it can't be moved?
Did you put some Exante in the trap?! X