WWYD re a button coming off a coat described as BNWOT?

[mygirllollipop]

As the title says, WWYD if a button came off a BNWOT coat on the first wear?
TIA

Sew it back on?

TBH I've bought things brand new (from shops) and had buttons fall off pretty much instantly.

Sorry meant to add does it not look brand new?

I've had buttons come off totally brand new clothes bought in shops on their first wearing.

I check all buttons on all new clothers I buy and reinforce the sewing as manufacturers don't secure them enough.