I have a hummingbird helix 5. I had approximately 50 waypoints of a couple diffrent lakes in my area. I went out of state on a trip and marked more waypoints. Somehow I lost all of my local lake waypoints. Will the unit only hold so many on hard drive? I know backing them up is best option, but trying to figure out what happened to them. I will be backing up on a micro sd card, hummpc is out of the question because I don't have acess to a computer besides work. Thanks Jason