Rear suspension wishbone

I replaced the rear suspension upper wishbone today and the passenger side bolt will not tighten, it gets snug then you can feel a slip and it never fully tightens. I assume there's a captive nut that came loose. Can I access it if I remove the rear seat? Thanks in advance!

Ken

If you search on here I think I vaguely remember reading a post where someone drilled a hole from above to get to it.

I’ll post this just to warn others of the danger of trying to force the bolts back in on the front corners of the upper rear control arm. Don’t do it! You’ll end up removing the rear seat and cutting a hole in the floorboard to put the captive nut back in place. Use two jacks on the rear end so you can tip it front to back and a ratchet strap to pull it side to side. Lesson learned the hard way!

Amazing how a simple job can grow into a days hard labour!