Or does the dog just stop and do it where it wants to?

Last night I just put my bag down on the floor while I locked my bike outside the pub. One of the bar staff was taking the pub's dog out for a walk and the guy stood next to me looking in the opposite direction for a few seconds. I looked down and the dog was between us cocking his leg over my open bag and started pissing in it. They both then moved on.

I was kind of in shock..I did shout out but was it the owner's fault or did the dog just randomly choose my bag for a piss?

The bloke with the dog was playing pool inside so I did pour a bit back from my bag into his glass. ACtually it may not be his. It was next to him but it could have been 6 others. They looked like wankers so it's ok