I would look a couple more days, if you can't find them call WDW and ask for replacements, they should have the ticket numbers on file if you ordered over the phone. One time I did not receive my MVMCP tickets, lost in the mail, and they replaced them.
I never lost MNSSHP tickets, but one time, when I was 17, I started packing late the night before I was leaving for a one month trip to Germany. Of course my mom tried to get me to do it sooner - but I didn't listen...and I could not find my PASSPORT anywhere!!! I was up all night, until 6 am the next morning, searching the entire house for it (without waking my parents!!).
Fortunately, I did find it, but I learned my lesson about packing early from that trip!!!
You'll find them -- if not, I'm sure you'll be able to get them replaced....