Very common. You can even easily find pirated assets on reputable marketplaces, like cgt, or ts. The more popular and higher quality your assets are, the more chances that they will be pirated sooner rather than later.
If you find your stolen assets here on cgt, it's easy - you just report to the support and assets and possibly the thief will be taken down. If you find them elsewhere, especially in places like telegram, you're basically out of luck. You can try to fill takedowns and if the site is semi decent, you may even achieve asset removal, but it's just a matter of time when it will reappear in ten more places. As you correctly guessed by yourself - it's just inevitable part of being creator. Since some time i prefer not to look for my models online - what you don't know doesn't hurt you.
