I worked in the US. for 3 years under H1-B visa and I returned to my home country in 2005. Long time ago, I heard that in this case, social security tax and medicare tax can be refunded. Is that true? How can I claim for the refund? And is there anything else I can claim for in this case? Thank you.

I do not think so. Anyone under an H-1 visa is subject to SS and Medicare taxes. If they do not work long enough to qualify for the pension (minimum of 40 quarters, or ten years), they forfeit their contribution.