You get home, still pondering your new appendage, and decide that you might as well get to bed. You aren't entirely sure that going through life with a trunk would be a fair trade for the benefits of what is basically an extra limb, but you can sleep on it.
You dream. There's a field, a crowd of people in it. You're mingling, completely human. Life of the party, you might say. You sneeze. Your nose explodes outwards as you do, instantly lengthening into a trunk. Screaming... panic... someone's pointing at something. Pointing at you. They scream "MONSTER!" and then try to run, but your trunk grabs them, chokes them. You want it to stop, but it squeezes them tighter. There's a snap.
You wake up. It doesn't take long to realize what the dream meant: the trunk is more trouble than it's worth, you'll have to get rid of it. Your mind made up, you begin to stride out of bed... and fall as you find your face tethered to some big gray mass. No, wait... that mass IS your face! It looks like, as you slept, the part of you exposed to the latex finished fully turning into an animal part.
Where once your trunk had at least matched your body in both color and size, you now have one that looks like it came right off a full-sized elephant. Covered in rough grey skin, it must be a good six feet now, as it droops to the floor. It also seems much heavier, certainly more than you could hope to carry on your own (though the trunk's own muscles still make it at least possible for you to stand and move). From what you can tell, no other part of you has changed. Hopefully, the transformation is limited to where you were touched. Then again, some elephant legs to help carry this thing wouldn't hurt.