Pentax is nice - I have a K7 and K3 mk1, I defected from Nikon when the D300 replacement failed to materialise and the K3 came out, got the K7 for under £100 for something to use in the rain and not worry about it imploding. I'd started out with a P30 when I took up photography back in the day, so it was like coming home.
Anyway, searching for a way to find your serial number from a jpeg, I found this below site:
http://www.stolencamerafinder.com/
Put an unedited jpeg from your K50 in and it'll search the web for images with your cameras serial number. Might find your own pics, might uploads from whoever has your camera now. Looks like it'll provide your cameras serial number at the very least, K50 is supported. Good luck.
EDIT - I tested the above site, but it didn't work for me
BUT told me to use the below which worked:
http://exif.regex.info/exif.cgi
There is "Internal Serial Number" and "Serial Number", the second one "Serial Number" is the one printed to the bottom of your camera, ctrl+F to find it there is SOOOO much exif data that comes out it's awesome. Take that number to all of the local pawn-shops / local second hand electronics places they have to keep a log of s/n and should not accept any items that have had them scratched off etc.