Engine knock after oil change

Hi,

I have a 1998 Ford Probe with 133,000 miles on it or so.

I just had the oil changed at a local service center (had them change it while doing brake work).

After getting my car back there is now an engine knock. Could the service center have caused the knock? (A quick goggle search suggests that if the engine was started without having put enough oil back in that that would have caused it - but that seems extremely unlikely for a service center to have done.).

I had paid for the work but didn't pick up my car till a few nights later, while the center was closed due to not having someone to drive me over till then.

I took it back in this afternoon and explained that I had started hearing this noise when I picked it up. (Not having heard engine knock before, when I explained it - I thought perhaps it was a loose fan belt or a bolt rattling or such). The service guy stated that on the post oil test run the oil change guy had mentioned a knock when he drove it after changing the oil.

He went out and listened and confirmed that what I was hearing was in fact the knock mentioned by the technician.

I partially suspect a error on their behalf due to

1) it not being present before the oil change

2) the last time they did an oil change the repair individual had failed to rehook up my oil pressure gauge (I mentioned it and they had thought it was like that when it came in, but after I insisted it wasn't they checked and confirmed it had just not been not hooked back up).

Thanks