The other day I either got scammed/hacked or did something to my ERC20 wallet that made it inaccessible.
Its impossible that you can't access it if you are using a non custodial wallet. Since the only needed is the private key or Mnemonics key in order to access the wallet. Cause you can't change the private key forever.
So my question is - did I get scammed (ie contents of my clipboard with the private keys get intercepted by the Telegram chat participant) or is it possible that I inadvertently altered/moved my tokens to a different address via the above site.
Most likely that you've entered your PK through a phishing site where they access your account and transfer your tokens since you said yourself that you didn't do any transaction. You must be careful when dealing with this kind of giving your valuable PK cause one wrong move to give it to a malicious site it's over already.