The computer in question connected to the internet. After cut and paste files and folders onto external hard drive; the external hard drive was safely removed from the computer in question. After that the external hard drive was plugged into another computer without internet connection, the cut/paste files folders "disappeared" but the external hard drive space is occupied by the size of the cut/paste files folders. No matter what I do the cut/paste files and folders can not be seen in the external hard drive. I plugged the external hard drive back into computer in question, also I can not see cut/paste files and folders: they "disappear". They can only be seen inside Stellar Phoenix Windows Data Recovery Professional after I let this software scan the external hard drive. Back outside this Stellar software in Files Explorer, the cut/paste files and folders still can not be seen. The only way to recover these files is through recover option inside Stellar software with takes two or three days to recover 300 gb of data.
The computer in question was scanned with Avast Premium latest definition and latest version. But Avast did not find anything.
Please instruct me how to prevent these from happening. Three days to recover 300 gb worth of data.
Thanks in advance.