911SC seat bolt question---> Trouble Assembling Seats

[groovzilla1959]

All,

I purchased nice pair of original 911SC stock seats on EBay. Seller is totally worthless and can't explain or answer my simple question and considering he disassembled the seats and packed the bolts I can't understand his lack of follow thru.
The seats were shipped with the seatbacks unbolted from bottoms and the wire on each seat which controls lifting seat forward is attached to respective bottom and all is good there.

There are 3 bolts that attach seat backs to seat bottoms - Total of six. (photo 1) Seller sent the set of 6 bolts and one of the black blots w/screw head is missing/not included.
my issue---> there are 2 bolts that connect the seat bottom on the same side as the round handle for adjusting seat back angle----> There is 1 black bolt w/screw head on the opposite side of seat which attached that side and those screws are fine and in place. (Photo-2)
Photo 3 shows the problem hole with red arrow- 1 bolt threads in fine and tightened - **the other bolt hole has no threads and the bolt just floats in that hole? The seller said he just unbolted them but that isn't possible - there must have been a nut or some sort of fastener to hold it.
I can't get fingers inside to use a nut or similar so anyone know how these bolts get installed?

Can anyone chime in on a solution??