Or is it possible that this seed leads to another wallet not mine?
It would happen something like this:
- You already have a wallet called "default_wallet" (maybe from a previous install, as Electrum doesn't delete wallet files when uninstalled)
- You create a new wallet, say "wallet_file_1", and write the seed down
- When you re-open Electrum, it opens "default_wallet" instead of "wallet_file_1"... you use this wallet to send/receive
- Your computer harddrive breaks
- You reinstall Electrum and restore seed... but it is restoring "wallet_file_1" which has no transactions or coins
However, without the original drive, it's impossible to check my theory (you could simply look in the "wallets" folder and see if you have multiple wallet files)...
This is why it is ALWAYS important to make sure that when you create a new wallet, you check that the seed you have written down is working correctly and restoring the wallet with correct addresses before you start using it!