Thanks for helping this guy out, especially since it is so hot and food must be scarce in downtown Toronto.
Have you put up posters in the immediate neighbourhood (at Starbuck's too)? Just put 'cat found', with the area he was found in, to avoid scammers and ghouls. Put up lots of them because they get torn down by idiots.
Did you call the SPCA to see if he has been reported missing?
Is he neutered (they still have their balls, but noticeably deflated
)? If not, he has probably just wandered off, looking for lurve. I've rescued a few cats and only once found the owner, but since he is so sweet and comfortable with you, it's likely he hasn't been on the lam for long. Please give him a chance. I'm not sure if the Toronto SPCA is no-kill, but I hope it is.