I'm sorry to hear about your problem, Tindomul.
The only microsoft office program that gives me trouble is Excel; sometimes, it refuses to graph anything right. My Bio lab final this semester had an excel section, where we had to graph data and turn in both the spreadsheet and graph. To cut a long story short, nobody in the class was able to graph the data, because the program kept screwing up.
While I'm not sure how to recover the lost powerpoint, I can tell you how to avoid the same problem in the future. Try saving multiple copies of the document, and keep some on your computer and some on a flash drive. Also, make sure you know where the document will end up after it is saved. I've had trouble finding files in the past because I saved them to weird places.
Good luck!