I am sorry for what I am about to type.
Due to the advanced state of decomposition that 2 weeks in Texas temperatures unless she was in some type of container (bag, box or tub) or wrapped in something resembling a shroud (remember the search warrant fabric and blue string) her body would not have been in shape for a quick move. The odor, sloughing of the skin, bloating, putrification, and insect infestation would all create problems for anyone attempting to move her without protective gear and tools. To then conceal her small limp decomposed body into the culvert would be even more difficult.
If she were moved by a human, it would have to of been in the early days. There is more than one reason you see LE wearing those white tyvek outfits with shoe covers and gloves. Not only for evidence preservation and to prevent crime scene contamination but everything that comes into contact with a decomposing body and it’s by products, absorbs and retains that horrific odor. As bad as the odor we have all experienced driving by old road kill can be, human decomposition is much worse. Only pigs have a similar odor. It stays in your nostrils sometimes for days and it is an odor that is so “thick” you feel like you can taste it. It is bitter and acidic. I only say this not to be disturbingly graphic, but to show how desperate or deranged someone would need to be to move a body if they didn’t have to.
If those claiming to have previously searched that culvert are not trying to get their 15 minutes or are not mistaken or didn’t miss her when they looked, then I think any move that might possibly have been made in the last week might have been made by animal predation.
JMHO
Was hoping to see a theory as to why her *maybe* not being in the culvert until much later might let Dad off the hook. 
