I think I have an unresolved journey on my Oyster card.

I was travelling from work to Waterloo and missed my stop, getting off
at Southwark. I decided to walk back to the mainline platforms via
Waterloo East. However, I don't think there is an "out" barrier
between the Tube platforms at Southwark and the entrance to Waterloo
East. At Waterloo East, as it is a mainline station, I automatically
used my London Stations season ticket to get through the barrier (the
barrier wouldn't accept the ticket but the ticket inspector let me
through). In retrospect maybe I should have used my Oyster to
register an "out", but I didn't want to register an "in" when I wasn't
going to be travelling from Waterloo East.

Anyway, will this be an unresolved journey and what do I do about it?
Unaccountably, I don't seem to be able to check my Oyster card usage
online. Can I do so at a Tube station, or is phone or email the best?

Apologies if there have been lots of similar queries, but there's not
really a lot of information on the LUL website.

Cheers.

Phil