Passport Missing

I was filling out an immigration form, and need the expiration date of the passport. I looked into the drawer where I store all the foreign currency and passport, and it was not there! Dunno what I did, but the last time I used it was when I went to China for customer audit back in August or September (gosh, I don't remember). I had to use passport to leave Taiwan, and China passport to enter China. Now the China passport is there but Taiwan passport is gone.

Had a quick check with the travel agent today. I will need to file a report at the police station, and then fill out application form. The lead time will be one week. Glad that I found this issue ahead of time, and not the last minute when I had to apply for Thailand visa. The restriction on the plane ticket is no change permitted...