piztaker:
It was only $1.50 but it's no longer by my username. Can I have it back?
Your winnings is the credit amount(s) you have won over time.
You may be referring to Credits, which is located above PLAY NOW on your profile. If you no longer have the 150 credits ($1.50), it may be possible that you bought some or someone else used your account, credits don't just disappear.