Dealing with Piracy of Your Music
Music piracy or illegal use of your music is something that every composer needs to struggle with these days. As soon as you publish something, there is a chance that somebody uses it without your permission and without paying you. There is no effective way to prevent this except not publishing any music at all. Trying to track illegal use is practically not possible to do effectively, also not for any PRO you might be member of.
However, you should also be aware that the financial loss is usually quite low on these instances. People who use music from the internet illegally in their projects/videos will most likely not have the money to pay for it anyway and businesses who do have the money will usually not use music illegally (unfortunately with few exceptions). So while it is understandably annoying to see your music being used without ever noticing or paying you, there is not really any sense in getting upset or wasting a lot of energy on it.
In my experience, the energy and time it takes to track down such occurances and do something about it are only worth it in major cases or where you strictly don’t want your music to be associated with (e.g. doubtful political campaigns etc.). Hunting down every 15-year-old kid who uses your music on Youtube videos will likely not be worth the effort. Unfortunately this is just part of the way how people’s understanding of music and its compensation works these days.