Thank you all for your replies.
I will try to contact Microsoft to find a solution
Even if the site is still active, which is unlikely, and even if you had a few bitcoins in your account at the time, which were worth only a few dollars, it is unlikely that the site owner would have left such an amount of money in a dormant account for so long. It's worth noting that the value of 1 BTC soared to over 60k USD in 2021. So that money is most likely gone long ago.
Exactly, even if that site is alive the chances are almost zero as things have changed in the last 12 years. When OP got those free bitcoins, it was worth less than 1 dollar, and now they are worth hundreds of thousands of dollars, asking the site to pay for those bitcoins will never happen.
OP, those bitcoins were once in your possession, but since you don't withdraw them to your non-custodial wallet, if you can find them again, they will have no reason to pay you. Their value has changed a lot, no one gives you hundreds of thousands of dollars for free.