2013 Toyota rav4 automatic v6 failed driveshaft after mechanic left subframe loose

2013 Toyota rav4 loose sub frame

Ok so my lower control arms needed to be changed, mechanic did them both. I felt vibrations right after.. took it back but before got underneath it and found loose sub frame bolts on both sides. I read that you need to loosen sub frame to change lower control arms... Now mechanic says my driveshaft has failed but also admitted to leaving the subframe loose accidental but swears the two are unrelated.. is this possible? Seems to reason the subframe being floppy can't help the drive shaft's alignment but I dunno that's why I'm asking you reddit! 🙏