What should I do?
Discover what is compromised in your system.
Format your computer.
Buy a hardware wallet.Where did you stored your seed? In a paper? If not, that is a mistake.
Can I do anything to return the money?
No.
The wallet profile was missing on the PC, as well as the passphrase to restore it. I don't think it's my PC. I believe that the actions were carried out on a third-party resource. Does Electrum have tech support to check this? How can I communicate them?