Sounds like the drain froze. When in a heat pump mode, the exterior coils can form ice. Typically the unit after running a certain amount of time, reverses cycles (without the fan running) which causes the outside coils to get warm. This causes the ice on the coils to melt. If it's cold enough that water might freeze up in the drain tube and the pan might fill.
While I haven't had the water issue, I have had the outside coils pick up so much ice, that the defrost cycle can't melt it all. What subsequently happened was a total ice up and we came back to the trailer only to find the temps inside to be pretty cool. This was in 100 humidity with the temps in the low 40's.
'04 Classic 30' S.O.,'03 GMC Savana 2500,'14 Honda CTX 700