BMW E90 320i Oil Pump GONE!!!

[QA]

Has anyone come across an issue with oil pump failing without warning on E90 320i! Mine went in for a oil service at a local garage last week. Its done 87k running fine until I went to pick it up. Started the car up within 30 secs oil light came on. Shortly after its started to sound like a old diesel and them should a tapping noise. Showed it to the mechanic who was confused to why it was asking for more oil when it was full. After a few hours the mechanic decided to stick it back on the ramp and take sump of etc.... Anyway now the engine will not start and have been told I need a new engine.
This is all very strange and don't understand why this would happen. I have had BMW's in the past and loved them to bits, but this have totally put me right off them. Any suggestions would be helpful to whats best way to sort this issue out. I am pretty sure BMW CS wont be very helpful unless I pay them to sort it out. The engine on mine is a N43 which seem to have common issues.

[QA]

Its was showing full.

[QA]

Showing full on the dashboard as these don't have a dipstick. A red oil light came up and now there is no presser in the pump which seems to have ceased the engine up.

[QA]

Thanks guys for your input. I am really just confused to whats gone on. I am now left with finding a new engine if anyone can direct me to a good supplier. As for getting a oil pump its not worth it as the whole engine needs to be dismantled and more costly.

[QA]

Well getting the garage to admit its their fault will be hard. All they are saying "it can happen at any point without warming". The engine was running for a few minutes and the mechanic opened the oil cap and check it was spiting oil. This shows the pump is working. Im no mechanic so unsure what check would have been done.
They did put ur back on the ramp and drained the oil out while i was watching. It was full amd filter was taken out to check also.

[QA]

Thank you REALIST123 for your input. I don't no how I would prove that is his fault unless there is a BMW master technician out there. I did speak to Steven at Lloyd Carlisle BMW who has been very helpful and he said sometimes the plastic guides on the chain break off. If this happens this can block the pipes to the pump etc. Unfortunately there are 100 miles away from me.

[QA]

Turn7 is going to be very very hard to make the independent garage admit its there fault. Would removing the oil pump and having it tested to see if its still working, prove its not what they say it is!

[QA]

How do I move this post? Sorry im new too all this!