The correct procedure for removing or renewing a calliper nipple is:

A bit of torque as if tightening, then a spot of WD 40

Leave for 5 or 10 mins

Try to undo - if not working, repeat above

If still not working

Then heat nipple with oxy/act torch, quick cool down with water and hey presto it will come out or undo

Procedure is if you need to do above then new nipple is inserted.

I agree with previous post - you should have asked for the original calliper so that you could at least see the sheared calliper, you would be able to see if nipple had a stress fracture (component metal defect) or if it a complete break through brute force.

I always ask to see components that have been replaced if I suspect foul play!

They should be offering some good will on this, if you do not ask you are making it difficult for everyone else for future scenarios. 'There is thunder' then 'There is the warble of a V8'

SD4 HSE Fuji White (my car): sidesteps, door protection
Golf 2.0 tdi White (wife's car)
Triumph Stag (my 1975 V8 toy - 37,600 miles... Just started its 2nd restoration... had it since 1986)

Tiguan Summit (gone, but nice car)
Porsche Boxster (gone, it was too fast)
SLK (gone, did not like it - lost loads £s)
Discovery Cairngorm (gone,very tractor like)
+ loads of other cars

You said it.....you were mugged! (GONE) FL2 2008 SE (manual) Santorini Black, the expensive one
(LEFT WITH) 300tdi Defender 90 the cold, reliable & sensible one