Yea, that's pretty rare. Nearly impossible to board the Ferry without your TVIP. You guys must really float under the Radar!
I was not able to even buy a Ferry ticket before showing TVIP. Nice Move!
I think OP is referring to "Sayulita" (little town just North of Puerto Vallarta). ?Tu conoces, no?
IMHO, do nothing. It's unlikely you will ever be asked for TVIP. I hope you have your Mex. tourist Visa? That and your passport is all that you will ever have to show in most cases.
Few tourists in NON Mexican vehicles that far South means light enforcement or even knowledge of TVIP rules. If you were heading South on Mex. 15 near Sonoran/Sinaloa border, then you might be checked on the road.
If you are asked for TVIP, simply say you lost it. Out on the road there is little they can do. Getting a TVIP now will probably be a major PITA as there are few Banjercito offices to handle this. Most likely they will send you to the border or ... they may attempt to fine you, maybe confiscate your bike.
So, IMHO, just continue on in ignorant bliss. Chances are you will be OK!
One problem could arise if you exit Mexico into Guatemala. Not sure how that works these days. Sjoerd will know more on this. But DON'T tell Banjercito at the border you LOST IT, because you won't be in their computer ... so may create problems. Dunno on this one. My friend crossed with expired TVIP
1.5 years out of date, was fined $300. YMMV.
If you exit Mexico into USA, there is NO TVIP check at border, by either Mexicans or USA. So no worries there. (TVIP holders must stop to turn in and cancel their TVIP and get deposit refunded to them)
With no TVIP, you simply exit Mexico and line up at USA border check. HSA folks only want to see your passport.
Good luck!