Welcome to the big boy world of adulthood. Crap rolls down hill and adults are always at the bottom.
You will find somethings are best done face to face, this is one of them. Go down to the DMV explain to the nice lady what the problem is. Play the “I’m a poor college student” card and I don’t know what to do. The nice lady at the DMV will walk you through the process to get the sticker. Maybe you will need a duplicate title, maybe she can find it for you. Take a digital photo of the registation currantly on the boat and print a picture so she knows what you are talking about.
It’s really all not that painfull but it’s one of those things you better get use to doing. Dealing with the government in one form or another happens quite often.
Good luck.