When using the ladder, the "pick up ladder" placeable appears where you start from rather than the destination end, making it impossible to retrieve on it's own once it's used.
I recall seeing in another thread that ladders are picked up from the bottom of a cliff, and ropes (grapple or not) from the top. Horizontal grapple ropes are picked on the chasm side opposite where they were fired from.
I didn't think it was a bug either but another veteran told me it was. If it's not a bug I may post a suggestion it be changed.
This is clearly a bug, because it allows you to put down a ladder from the top of a cliff, yet does not allow you to collect it after doing so. This is because the retrieve ladder placeable is set where your character is standing on the plane equal to the bottom of the ladder. This means that it always appears within the cliff or wall you are standing on. I do not see any reason why someone can only collect a ladder from the bottom anyway, out side of ease of scripting. If you are strong enough to carry the for miles, you are surely strong enough to lift it rung over rung up a short cliff face.
I think dropping a ladder down a cliff is probably easier than hauling it up, but yeah, anyone strong enough to go bopping around the caves with a whole ladder could haul it up with ease.
Logistically, I would expect something like this kind of ladder (//%22http://www.pplmotorhomes.com/parts/bike-carriers/gpl-ladder-half-open.jpg%22), folding in on itself. Chop it in half vertically, get another one (or half), and taper the legs such that they can fit inside each other and stack to whatever height. Complex and time-consuming, but probably the most rational way of shoving one in a backpack.
I'll consider if I -want- to add a retrieval at the top end. No promises.