This is going to sound kinda odd, but... If you turn out all the lights and use a bright flashlight (old bulb style works best) shine it at carpet level and the spring will not only be shiny but will cast a shadow that looks different from all the rest of the carpet. This only works of course on low or medium pile carpet. If you are stuck in the 60s/70s with the shag... well just get a new spring.
Ok, I found a few new ones... gonna save the best for last, hopefully I won’t get in trouble for it... Ok so here is what non rails think when they hear us talk.