Had my D2 tdi in the garage for a new clutch,duly fitted and off I went after they had problems and replaced the hydraulics.
Did about ten miles and on arrival at home noticed a pool of oil beneath the car,checked and found it to be from the bell housing/engine join,it dumped the entire engine oil out.
Added a small amount of oil and that ran strait out.
Anyone else ever had this,the leak is obviously from the crankshaft seal but suddenly I wonder why.

Have seen similar when bolts have been fitted in the wrong order in the bell housing and they have punched through into the sump

Where there's blame, there's a claim I think. I hope you can get them to put it right for you.

As @DanClarke says, this clearly can only be their fault.
I would suggest you don't drive it at all, get them to send someone out to look at it, and then take it straight back and fix it.
In fact I am amazed you didn't lose more than just the oil. If the oil pressure warning light did not come on then you cannot be seen to have been to blame in any way as you acted as any reasonable person did.
Depending on how well you get on with the garage, and even then, I'd be recording conversations either by having a witness there or some other means so that they cannot squessze out of getting and fitting a new sump, at the very least.
What a barsteward, all my sympathies mate. Long time since similar happened to me and it still rankles.

UPDATE The problem turned out to be the stupid idea of the TD5 engine have rubber seals on the botton bolts of the bell housing as the bolts go through into the sum as per the transit engine.One bolt had come very slightly loose probably as a result of the seal getting caught.
All put right by the garage after they checked out with the main dealer if this was the problem.
So alls well that ends well.