Here's where it is and what it looks like on the '86-up cars and quite possibly the '85's too:
It's attached to the inside edge of the passenger side deck lid hinge box.
And this is what the single black connector for the '85 should look like:
Edit to add: It's quite possible your deck lid has been changed from the original, and also possible that your car never had the complete wiring harness installed either. To know whether your car originally came equipped with the power trunk option, check your RPO sticker under the front hood on the driver's side wheel arch for the code A90. If it's not there, then that's probably why you can't find all of the wires.
[This message has been edited by Bloozberry (edited 07-22-2013).]