It looks like hes got a bumper sticking out to at the bottom, so to cause that scrape above the sticking out bumper, you must have to hit it with a bit of force to push the bumper in, so your car could scrape it above there, and also crushed your wheel arch in as well, as with that protruding out, thats the only part of your car that would hit it just by scraping, so id say someones actually bumped into his car, probably who was gona park there where you have, then quickly buggered off to another parking spot, then you innocently park there, he comes back, you've hit my car, ive seen that happen many a time, or he knows about it as its been there a while, and is just trying to pin it on you.