RAW? it works, no question. as
@GMMichael said, the spell only targets a single creature, and the artificer is physically incapable of targeting the druid anyway. balance wise i don't even think it's that bad - it requires a daily resource (albeit one that gets fairly cheap at higher levels) and a saving throw that, as a swallowing creature, the target is probably at least decent at anyway.
logically? well, logically, we're kind of screwed no matter how we approach this, and it's entirely the spell's fault. if we just take the spell how it works as a single target spell, then we can assume the spell works by magically selecting the target creature (think the lasso tool from photoshop) and moving them...except the flavour text specifies it warps
the space around them, which seems fairly indiscriminate. but if we focus on the flavour text, suddenly it being a single target spell makes no sense, and it SHOULD be an area spell with a radius of at least 10 feet, since it can target any size of creature. but if you select the area such that a creature is only partially caught in the area...what happens? mechanically it'd probably just be like any other area of effect, but we're only operating on internal logic here, and internal logic suggests that if we only warp part of a creature such that the warped part teleports...welp, now we have half a creature in one place and half in another, and suddenly the spell is even MORE broken then we were worried about it being!
so i'd let it work, personally, because i don't really think it's that broken, and trying to delve into why it logically "shouldn't" work just creates more problems. if the dm decides it shouldn't work anyway, though, maybe they should consider giving the artificer the chance to figure that out BEFORE they use the spell? i mean, it's not like it's targeting a creature's immunity, it's just a basic use case of the spell.