Haha! It looks like they somehow write literal zero instead of numeric. In programming (e.g. in C and C++) it is a common way to quickly "erase" text by placing numeric zero as the first character. Because zero marks the end of text. If you mistakenly use literal zero - it will just appear as you've replaced the first character by zero character. Nice. I will have some lulz tomorrow with co-workers
MS Dos/Windows used to put a tilde (~) at the front of the name listed in the directory, overwriting the first letter of the name, just like we're seeing here. So "My Dog.jpg" becomes "~y Dog.jpg". That entry doesn't just give the name, but also gives a location on the the disk where the actual file resides. They do something else to make that space available again--they typically do something to put that space at the "back of the queue" for reassignment, so that it won't actually be overwritten for a while, until the machine has nothing less recent to overwrite.
The file recovery software that came with the Microshaft operating system (and maybe still does) would check to ensure that none of the actual file got overwritten, then ask you to tell it what that first letter originally was before they replaced it with ~. Once you supply that letter, the directory entry became visible again, and the actual data (stored in some other part of the disk than where the directory entries were) would then be marked as in use again.
(I think modern (Post Windows 95) systems actually do something different. They move the file's directory listing to the "recycle bin" and there it sits until you empty the bin. Even then, perhaps, all it does is put the tilde in and it works like I'm describing. I just don't know.)
All bets are off, of course, if you "erase" a bunch of files and then defragment your hard drive. When you do that, data actually gets physically moved from one location to another rather than just de-listed, and anything marked as presently not in use is up for grabs. So the data that you "erased" will more than likely really get overwritten. Similarly, a low level format will trash the entire structure.
A lot of this is not true for SSDs, by the way. There's no motivation to "defragment" them because an SSD is truly random access. If you read sector 0 then read sector 1,000,000,000, it's just as fast as reading sector 0 then sector 1, unlike with a hard drive that has to re-position the read head in the first case but not the second.
An analogy (which will date me); imagine you record lots of music onto cassettes. But when you're tired of the mix on a cassette, you don't actually erase the cassette; rather you just take the label off and throw the cassette in a bin of "blank" cassettes you can record different music onto. If you actually put it at the bottom of the bin when you do that, you're operating like a Microshaft system's hard drive. It's possible for you to find that cassette and put the label back onto it if you change your mind, but wait long enough and you'll eventually get down to the bottom of the bin and re-use the cassette, and THEN it's gone for good.