I couldn’t immediately wrap my mind around the situation.
If you have any of your receive addresses, you can look them up in a blockchain explorer (example) and that maybe could possibly provide some leads - but it’s a long shot. You’d also know if there have been any new transactions…
The moral of the story: don’t trust online sites! Run your own full Bitcoin / AltCoin nodes and keep all your coins there.
You can still run a full portable Bitcoin node with full blockchain from an encrypted 256GB (quarter TB) USB drive, but a 1TB USB drive only costs about $50 and would leave plenty of room for growth and for alt-coins. It is ideal to keep several copies of such drives, all encrypted. One can be your active copy that you use to catch up with the blockchain and make payments, and others can be clones you synchronize once a month and store in different locations: your fireproof safe, your car, your office, bank boxes, etc.
You can even make it a bootable USB drive running Linux, so you can use it from any computer and nothing on your main OS installation can maliciously read the wallet and steal your coins. (Although hardware-level hacks are still theoretically possible.) Shut down your computer, attach the USB drives, boot into Linux, type in the LVM password, catch up with the blockchain, rsync to your other USB drives, detach USB drives, and boot back into your main OS.