Mobile .Datein disappeared?

I have copied to my phone, directly to the internal memory, the .minecraft file. After I arrived at my other PC she disappeared. I've tried this again with a. Mono file where the same happened.
So all the files with a dot in front of it disappear in the directory and I do not know why. What should I do? Does anyone have a tip?

Files do not just disappear like that. Mostly, the disappearance of a file happens when one cuts out badly or removes the phone too soon, before completely inserting it. What did you do exactly?

Nothing like that. I put the file in it and afterwards (after completion of the transfer) settled and connected to another PC. I've tested this with another file like .minecraft. Before that and it has been gone again.