PAYG timeout

I have a contract phone and a PAYG - I use the PAYG at times when I don't want to take my contract phone (like abroad or if I need to give out a number to the unwashed ).

Anyhoo, I turned it on the other day and it said invalid SIM (or summin) ... I had pulled it out to put another SIM in so I thought I might have broken it ... anyhoo, I finally got round to going to O2 today ... basically if you haven't bought a top-up for 6 months, then it dies ... I said .. Oh ... well can I have my remaining credit back then ... (£7.30) ... or at least transferred onto a new SIM ... "Sorry sir, we can't do that" ... ... so I said "basically I have lost my £7.30 then" ....

Now I can understand not keeping the number active forever, but robbing bar-stewards!!