I should clarify, the reason I brought up that the only reference to 'seeing' the target is made in the first sentence (i.e. Typically the flavour text sentence) despite no mention of restriction in the target entry is that if you assume that the line is indeed mechanical rules text then the question of whether magic missile ignores concealment is largely moot. Most spells can be targeted even if you can't see the target, which is where concealment comes in. If magic missile indeed cannot be used to target anyone you can't see, there is no question of using the spell to overcome any concealment since you cannot see the target well enough to fulfill the requirements.
To be fair, not being able to target somebody you sang see is how it worked in 1e, too, if you hold sway with that, despite the target entry having no reference to this unusual requirement