I was just thinking the same thing. Since we know this MH has been moved, we know it should have been registered with the MVD. (To make it into real property would require a permanent foundation and permanent attachment, and approval by the County Assessor, and this does not sound like the case.) It seems the thing to do would be to track the location(s) of the MH with the MVD and see if there was anyone missing from those areas. There should be transfers of the Title and Bills of Sale along the way. This probably would have been done, otherwise the grandparents wouldn't legally own it, and they could not have transported it on the highway when they purchased it. But surely the police know this!
This is what I think happened; someone prior to this young ladies grandparents buying this mobile home had it put on their property at which point it became real estate and the State takes up the title..it is no more. I know of this happening where a guy resold a mobile home when he had a house built and there wasn't a title... so it was sold with a "bill of sale." That just shows ownership to anyone who comes knocking. Since it was placed on private owned land it would have been added to the land tax on reassessment just as any outbuilding such as a barn is added. No, they do not have to have tiles and recorded transfers to move them. The department of motor vehicles only keeps up with the ones tags are bought for. It's just like buying a regular house and having a moving company put it in. There is no registration there. As far as requirements of how they are set up the law has required (since the 80's) that they be anchored wherever it's set up.
Hope this helps. It's tricky to understand sometimes because in the case of the guy mentioned above the buyer insisted on title which the seller hired an attorney to find and he didn't know where to look. No title could be produced. Because of all the complications of closing a mobile home most title closing attorneys will not close them anymore.