I often see creators note that they would like to hear from people when they are using their assets in a game, so that they can check it out. Optional, of course. And there are devs who do that, just as you have experienced.
I do not think that you can do too much more here, though. At least I do not see a simple way to really 'track this' (for example if your assets would fall under a very particular tag that devs would use when using it, so you can easily pin down which games have used it). I believe at the end of the day, it is just a matter of 'letting your art out into the wild'. You may stumble on it from time to time, but I do not think there is too much to force the issue.