Say there is a device that has a 1x/day lightning bolt spell on it that is activated when someone touches it.
Can a magus detect an enchanted device using InVi? Not as in detect what it does (that is lab work) but detect that the device is enchanted. If so, would that be based on the level 5 guideline - detect any active magic?
And, if that is the case, say the magus figures out (oh, dear grog, we hardly knew thee) that there is a lightning bolt effect on the device. Can the magus cast a suppress spell to prevent the lightning bolt from going off when the device is touched? The suppress guideline says active spell. Is the lightning bolt only active when the trigger fires? Or, because it is lying in wait on the item, is it kind-a active and hence eligible to be suppressed?
The more powerful the item, the easier the spell to detect it. The biggies might be noticed by spontaneous magic already.
Only if there is a magic effect active on the device - which in general is not the case. You need a specific spell to detect enchanted devices, as by the quote above.
Before it is cast, the lightning bolt is not active. But see
A spell sponted or invented following that guideline to suppress Hermetic Auram magic could affect the item and prevent it from casting its effect. See for an example HoH:S p.129 Quiet the Cursing Tongue.
Magic items blowing up those who touch them are costly and rare traps, and also need care to set up and maintain: so few magi might expect them, and prepare formulaic spells to handle them.