Sounds like your camper did MARVELOUS if you ask me. You made your mistake by not leaving the air conditioner run all day while you were gone. Not only that, if your air conditioner was turned off in the morning, it hit 102 degrees outside, and the inside temperature was ONLY 88 degrees... you have a marvelously insulated camper.
If that were my camper, and it sat in that temperature all day, the inside temperature of the camper would not have been 88 degrees, not even the 102 that would match the outside temperature. Like a pressure cooker, mine would have continued to bubble up, more likely, the inside of mine would have reached near 120, and starting the air conditioner that late, it would have taken all night for it to finally make it comfortable.
No, yours did marvelous.