I always carry poo bags too and I find them in every pocket, I don't always have a tissue though lol!
I noticed a guy with a bullmastiff, he didn't attempt to clean up, I just said I bet you can't get a bag big enough for that lot. It made him uncomfortable but he left it.
I get cross with my dog he always finds a pile and poos so close to it, ugh! trying to clean his up without disturbing the existing one is a right job. So called friends at work suggested I should pick up the unidentified pile too - I don't think so.
Sue