Old version ok, but which one? Do you know the number of this version? Is it a version below 2.0?
The only two things that's possible for an address that wasn't derived from the seed to be included is through
"import private key" for Electrum version v1.xx before v2.0 when it's possible to import to a HD wallet.
"import private key" for Electrum version v1.xx before v2.0 when it's possible to import to a HD wallet.
It would appear very unlikely that the wallet was created on an old version of Electrum. The OP claims they took a screenshot of their addresses when they first created the wallet on Tails:
Before all that, when I created Electrum on Tails I made a shot of all my addresses, here it is:
https://anonfile.com/097eY563n6/20190923_183206_jpg
There you see that damn address as second from the top
https://anonfile.com/097eY563n6/20190923_183206_jpg
There you see that damn address as second from the top
As you can see from that screenshot, it has the "filter" dropdown boxes on the address tab... this feature was added in 3.0.1...
Prior to that, the addresses tab was sorted into simple expandable lists like this:
Another possible, but somewhat unlikely, scenario is that the OP had created TWO (or more) wallets on Tails initially and, for whatever reason, didn't realise and only saved the seed for the first wallet. They subsequently sent coins to an address in the second wallet (created from a different seed). Once everything was deleted (when updating Tails etc), the second wallet was lost forever as the seed recovered the first (unused) wallet
