These things happen I suppose, it's how I learned, let others make the mistakes
I'm sure the advice from the mods in other cases was to email DJI support, I suspect they might send a replacement at a cost you cannot refuse (free ?).....But I could be wrong.
It's a part of the landing gear assembly. You would wither have to buy a whole replacement landing gear, or contact support@dji.com to see if they are able to provide that part to you. I cannot guarantee the latter is possible or without cost.
I had one of those little covers pop off during a flight, never to be found, and after some back and forth with DJI support EU I got a set of replacements. They have a team, in EU at least, that deal with "Small Parts Replacement" (SPR) ... maybe ask for that.
I lost one also and another coming loose, contacted support and got a complete set of 4 free in a very short time. Not real easy to pop in the replacements but did then put tape around the leg there to make sure won't pop out again.
Mine hasn't came loose yet, but I do notice that one of them is not flush with the landing gear. When I run my finger over it, it is off a little. I try to push it in a bit, but it flexes back to its original setting and is quite annoying lol