Well than this was different. The first time it happened, I had built a consist and it loaded into that slot of the missing engine. I had an older list that I wrote to keep track of addresses. Trouble was I didn't notice until some time later when I couldn't find that engine in the remote. When I tried to add it, I got engine error. I used the loader to find the address. I moved the consist out of it and the engine loaded fine.
Second time it happened, the engine disappeared. I notice quicker as I was trying to run that engine sooner (different engine). I reloaded it without the same error trouble if I remember right.
I just found it wierd that it happened at all. The first engine occured roughly when i added a new tiu without loading the engines into it. I just figured it was some kind of problem caused by me. This second engine happened some time later, I never justified it.
So, is this a system failure? The engine remembered it's address. The remote had that address available. I did notice that there was no trace of that engine or address until I reloaded. Not sure if this happens to anyone else. I still wonder if it's because of the new tiu and maybe I missed something. By the second engine's disappearance, I had previously reloaded each engine and built new lashups into the new "L" TIU to smooth out operating problems.