Outdoor Power Equipment and Small Engines - cub cadet serial # question

I have a Cub Cadet model HDS3205. I want to go to the Cub web site and download a .pdf owner manual. The web site requires model # and serial # input. Here's where the fun begins.

I've looked for my serial #. It's under the seat on a number of modern garden tractors. Looked there. Nothing. Next thing is some guy told me it's on the sideframe up front. Looked there. Nothing.

I'm very receptive at this point of ideas of other places that serial # might be lurking.

Let's assume worst case: my Cub has no serial # tag. What is the next logical step? I'd write Cub Cadet and ask them, but they carefully conceal their mailing or email address so no one can contact them. So, what should I try next?

There are 2 serial numbers. One is the engines and it is stamped on a plate on the left side (looking from behind tractor) of the engine.
The other is stamped on the right side of the reduction gear housing. Hope this helps.
P.S. The numbers are not the same.