Most likely the bulb you just removed, isnt making the proper contact when you twisted it back in..
You should replace the bulb first, it may have been damaged when rolling around inside the cover housing, Have you tried that yet?
Does the indicator light up on the instrument panel when you turn it on?
If the turn signal indicator doesnt even light up, then i would double check the power supply at the fuses, then the combination unit.(relay)
Its located just to the left of the steering column, under the dash.
If you think there is a problem in the trailer wiring it could be a problem trying to isolate the cause.
All you can do is start by disconnecting any trailer harness to start with, because it will feed into the rest of the system.
lol,,,no need for reaming,,,
You should be using a voltmeter instead of an Amp meter,,,thats probably what ya meant :-)
Change the combination flasher, if the wiring is not shorted, ya just saved a reaming!!
Best of luck my friend.
If you have further questions on this, please feel free to reply.
Thanks for asking!