Your toiletry case is probably what set off whatever alarm/x-ray check or whatever they have going on that caused it to be opened and looked at. Was the sticker on the outside of the case? Is that how you're sure it happened on the domestic segment?

My complaint has always been if they are going to search it and tell you its for your 'security' then they should really search it or just leave us alone. The normal modus operandi is a crappy 'show' job where most things are not even looked at, much less checked (e.g. i've had zippered compartments with obvious stuff in them totally ignored during an SSSS search ) Sounds like your stuff was actually checked -- cans opened, etc.

BTW - this might be better placed in the travel security forum, even though it said UA security on the flyer, the only 'security' that should go in your bag is TSA (they might be associated with UA at the airport - who knows).