Recently got a new commuter, a Kona Dew Drop. Today I took it out of the back of my car (kind of defeating the point I know) and the rear derailleur and replaceable gear hanger just fell off. There's no evidence of anything shearing, but I can't find the bolt to refit it which must have rolled away.
I've only ridden the bike 4 or 5 times on nothing tougher than a gravelly path so surely it should not have fallen out anyway, its never happened on my mounatin bikes which take much more of a battering!

I've got it booked in for 1st service on Tuesday anyway, so should the bike shop replace the bolt and refit it for free?
Thoughts?

Certainly worth asking them

yes how else could it have come loose except by being poorly fitted?

Not your, def their's. Although if they failed to check everythings tight before you got it then I might cut my losses and go elsewhere rather than complaining.

it's only a chainring bolt ffs, just ask 'em to replace it.

If you havnt fiddled with the bolt, and it hasnt been sheared, then it was obviously them not fitting it correctly.

It comes fitted from the factory, the wheel clamps it in place so may not have even been there at all, they'll just put a new one in, it's hardly worth them arguing about it.

Was the wheel off in the car? If so, you might have bashed the hanger when removing the wheel, causing the thread to get damaged on the bolt or hanger. I did that to my Enduro so have to fit the hanger every time the wheel gets fitted until I can buy a new one