He wouldn't have to. It was never specified that Alex was shooting through anything so the most logical course of action takes precedence (and throwing it in now after it's been brought up in the OOC would be PGing), and the fact that he could target the left shoulder specifically implies that he could see Arty when he opened fire, since the sheer amount of electrical power and heat being emanated from the sword would dwarf anything from Arty himself right now and screw up scanners. Thermal would only pick up the heat from the sword (since it's so much hotter than Arty's body), and EM would only pick up the sword as well (for the same reason).