It is up to the DM
As anticlimactic the answer is, at this point, it is not possible to accurately answer this question as RAW or RAI. The main problem are the spells at this point in time and the information about them.
The first problem that arise is about the plane that the mansion from Mordenkainen’s Magnificent Mansion ends after the spell expire. As far as the spell description indicate there is no indication that it even continue existing on a particular plane, much less a reachable one, after the spells ends. Furthermore, even the mansion cannot be said that it is Mordenkainen’s as a form of keeping some sort of continuity. The spell description talk about summoning an extradimensional dwelling not the extradimensional dwelling. Therefore, the first thing is to establish if the mansion keeps existing somewhere after the spells ends and that is up to the DM (in what plane exists, can it be reached by a spell, it keeps the same layout, etc).
You conjure an extradimensional dwelling in range that lasts for the
The second problem is which divination spell, or which spell, can be used to locate an object. The low level spell Locate Object needs to be within 1000 feet range of the object, and that indicates that have to be in the same plane. The other spells, like Scrying require to be in the same plane and, in particular with this spell, that is a creature.
Detect Object Describe or name an object that is familiar to you. You sense the direction to the object’s location, as long as that
object is within 1,000 feet of you
Scrying You can see and hear a particular creature you choose that is on the same plane of existence as you.
Even if the mansion still exist, you know the plane, have a mean to reach it and end within a 1000 feet radius of the mansion (or that Scrying also works on no-longer-living-creatures because DM) there is a third problem: where is the entrance? The caster decide where the entrance is at moment of casting and who can enter. Again, is up to the DM to determine if the “entrance” still exist in the mansion and can be open form outside while being in the mansion’s plane.
And a bigger even is the behavior of the servants. It is true that they were given corpses and they brought these with them (they have to fulfill all the wishes of the master/caster the best they can), but nothing state what they do with them after. They can throw them into another plane or even burn them. Speaking of servant, since you weren’t the “guests” are they going to be hostile for invading their property without the master/caster permission? Again, all of these things are up to the DM.
Finally, about the readings of divination magic; if everything is taken care of the reading would not be different from their normal reading. e.g. “The objects/bodies are outside of range”, “the corpses no longer exist in this plane”, and a list of reading that correspond to the moment, situation, place and spell used.