On GW decals

I just drybrushed the HH with a lighter color than the original and when i cleaned the brush, I noticed one of the "20" numbers on my hand. I rushed back to the model to notice the other was missing from the engine too. I didn't get to the tower yet, I hope I won't loose that, coz I've already done that earlier but put it back to its place with watered down PVA glue... The same will go with the new decals on the engines, I'm sure. Have You ever had a similar experience?