once you pull the thermostat out, you can check to see if it works by putting it in a pot with water and heating it up. You'll see it open if it is working. It would be great to have a thermometer - maybe a restaurant will let you borrow one and their stove - but if not, at least you can tell if it opens by the time it boils.
If you really doubt it works, leave it out, but remember it will take a lot longer for the bike to warm up.
God. Family. Motorcycles. Guns. Music. Books. Dogs. Beer. Baseball. Work. That about covers it.