I havn't experianced anything like that, but I did have a best friend how killed himself freshman year. Did it with a shotgun, speculation was because his mom was about to die of breastcancer and other problems in his life. He didn't leave a note or anything.

Idk, maybe it isn't in your mind but it could be a way for your mind to cope with your loss, I am really no expert on spirits but at this point I don't really believe they can interact with humans...