The first thing which I noticed there was that their surroundings fitted their symbols or motiv as Nobodies if you want to call it like that. Lauriam = flowers; Elrena = thunderstorm.
Until some minutes ago I thought it was pure symbolism, but now where I think of it, maybe the sceneries were somehow a trigger for someone passing by remembering them (subconsiously or not) and triggering this way their reapeerrance. For Lauriam it might be explainable with his keyblade, but I can't come up for any connection between Elrena and thunder prior her time as Larxene, but at the same time we learned less about Elrena than Lauriam, so there might be a connection we are not aware of yet. Furthermore in the case of a subconscious memory coming up it could fit with something what someone else said (and others also already had refferenced), that their memory loss wasnt caused by the pods, but because of something else. This else would be in this case, that the memory was only weak and so the recreation of their bodies wasn't in a perfect way.