How do I know a stray is eating the food I leave out and not a raccoon or something else?

My bf and I saw a stray cat recently who seemed pretty nice and came up to us, but we accidentally scared the cat away by stepping on leaves and the cat took off into the sewers. We made an outdoor cat bed with a box, an old sweatshirt and a towel inside with a bit of catnip because it’s been freezing outside and a Tupperware container with cat food about 10 feet away from the box. Both were left near where we originally spotted the kitty. After a few nights of the food being left untouched, the food has regularly been gone every night, but the bed does not look like it has been used. I was hoping the stray would get used to the bed so that I can eventually replace it with a trap, but I don’t have a camera I could set out and I’m not sure if it’s the kitty eating the food or something else. The kitty didn’t have a collar and I haven’t seen any other strays around the area, and my roommate reported seeing the cat while on a walk a few weeks ago. Since the kitty was already decently nice, I was hoping to check for a microchip and possibly re home since I already have a kitty. What should I do?