On 02/01/2014 00:47, Paul Corfield wrote:

They may be able to move the "errant" card under your main account - I
think you can have more than one card held on one account. Having
logged on to Oyster online I see you can add another card to an
account by entering the extra card's number and completing the
security question details from when it was first registered. This all
rather assumes you can remember what it was!

It's also possible to get the password reset by going along to a Ticket
Office and asking them to change it, though you may need to complete a
registration form to do so. Not sure how long that takes to filter
through to the online system however.