Sentence examples for lose count from inspiring English sources

The phrase "lose count" is correct and can be used in written English.
You can use it when you want to express that you have been counting something (usually a large amount of things that is hard to keep track of) and have become confused, forgetting the current number you have reached. For example: "I've been counting these coins for so long that I think I lost count of how many I've gone through already."