Sounds to me like you have experienced an "end of tank dump". This is when the pressure within your Co2 tank equalizes with the pressure outside of the tank. What is the pressure reading on the Co2 tank? Is it lower than normal? How long have you been running the Co2 cylinder and what's its size?
Also, I think I know what happened to the water in your bubble counter. When I first set up my pressurized system, I had filled the bubble counter fill to the top with water. Then when I turned the big nob to release Co2 from the tank (the needle valve was pretty much wide open) a huge rush of Co2 came flying out and guess what... no more water in my bubble counter. I think with the extreme rush of Co2, it was all pushed out of the bubble counter, through the hose and into my tank. If in fact you did have an end of tank dump, this could have happened to you as well.
Just a guess.
