I was thinking you could go into the console, click on the "light" mesh (the one that's missing) and get an object ID, then use that ID and load the plugins up in the CK (make sure you have multiple masters set), or xEdit (the one for Fallout NV) and lookup that ID. That'll might help you locate the record. If it's being overwritten within an esp it should show up, if not, it could point you to the mesh name that you can use to investigate further (bsa, etc.,.).
It's true if you have too many mods, the game won't load the meshes even if they're available. It's like, anything over a certain number, the game recycles back... like if it's 255 and you have 256, 256-255 = 1 so the first plugin reference #1, gets overwritten with #256- missing meshes, etc for everything in plugin #1 (which usually is the essential game file fallout.esm).