[JRTJH]

I would guess that the frozen sewer hose is a result of leaving a faucet dripping and that slow trickle of water through the hose has frozen and the continuing trickle has frozen on top of the frozen water....

How to fix it? I'd start with a couple of drop lights with 60 watt bulbs, build a Styrofoam "box" from three lengths of Styrofoam. Place the three lengths over the sewer hose starting at the end closest to the park connection. Plug in the drop lights place them inside the "Styrofoam box" so they can warm the sewer hose. As it thaws, the water/gray/black waste will flow down, into the sewer. Once that part of the hose is thawed, move the "Styrofoam box" closer to the trailer and repeat as long as necessary. You might be able to use some spun fiberglass insulation or even cardboard boxes to cover the hose and contain the heat from the drop lights until the hose is thawed.

Another option, if you have a replacement sewer hose is to thaw both ends and then just attach the new hose in place of the frozen one.

Keep in mind that if you "drip the faucets" you're probably going to have the same problem in a couple of days.