I'm a bit surprised that we haven't heard more of these stories from folks in New England.
If there was snow up and over the trailer's floor height, it's possible that the melting snow softened the floor where it attaches to the wall. If the plywood floor softens, the fasteners that hold it to the wall may have loosened and the floor has dropped down. If it was me, i'd apply construction adhesive to the area that has separated and drive screws through the floor, up into the wall's sill plate. Depending on the integrity of the floor, you may wish to add an additional piece of lumber under that separated area. I would use a 1 x 4 of exterior graded lumber or a piece of Trex decking. The plastic deck boards hold up real good to moisture.