On-foot materials (...which, yes, show up on the SRV HUD, but not when actually on foot -- annoying) that spawn at locations on the ground, indeed sometimes end up below ground or embedded inside static objects, depending on terrain.
(EDIT: I am sure you have also noted that now and again for exampe a cut-open-able compartment on say an SRV end up offset in space from said SRV, inside of it, or floating in the air in the vicinity of its designated place.)