I will throw out MO here.
He took her, not meaning to kill, but rob. Something goes wrong, she knows who he is, saw him to good, something. He is going to leave the next day. has to do something now. I originally figured a close dump location. This is just out of that range to fit in the time frame. So he does what he did, and leaves her in the shed, it was cold those weeks, I went and looked at the temp.
he comes back and now has time to hide it.
On a weekday, there likely wont be anyone fishing there. i assume he had an ice fishing pop up. Some fold right into themselves and are a sled. (look up eskimo ice fishing for ideas). Could have packed her in that, or in a sled with gear. Not out of the ordinary to pull a sled out ice fishing to carry all the gear, poles, auger, bait, tent etc.
Drills at least 2 holes next to each other. with a larger 10" auger it would only require 2 holes just touching. with a smaller one it would take 3 in a clover fashion or 4 in a square.
Again, not odd to see. I drill 2 side by side to fit the underwater camera down.
Drilled the holes, sets up tent around the sled and over the holes. Puts body down the hole. All the ice shavings are there from drilling the hole. Fills it back in (common courtesty ice fishing, so someone doesn't fall in or so the shavings dont freeze in a lump to hit with sno-go), smooths over the snow. it would refreeze in a few hours.
he packs up stuff, and leaves..... never rasining a flag, even if there were people there...
If it didn't sink, then there would be a chance of refreezing into the hole. I beleive though it would sink initially.
So, the holes are refrozen, covered in snow etc.
IMO he did not tow that shed there, not at that lake. The access is a fairly steep path down to the water. It would be impossible to pull it back up, that would be odd.....
If it was a lake he could drive onto, and had a shed / shanty, that wouldn't be that odd either.
as far as drilling in the middle, that lake is small. So, drilling in the middle, I would assume allows for a search of the whole lake from one hole, whereas if they started on one side, that would be a greater distance to the opposite shore.
I would guess that they found hair, skin something in the shed. And he finally spilled the beans.
All is way too much work for IK to do before he left town the next morning. It is just outside the time/distance factor to be the abductor, debit card theif and leave town in the same night. making the shed be the cold storage while gone. I would also guess that the death was caused by strangulation or blunt object, not a gun or knife.... IMO..
I bet there is more to come for other stuff he has been involved with, besides the kidnapping, access charges etc, now that he has a body in his shed. Might as well go for the big time at that point. i bet there will be a crime spree following his travel trail