I had a oil change done to my 2002 Ford Focus. When we took it in there was no lights. It took the shop and hour to do my oil change. About an hour of driving my car I noticed a horrible knocking sound in my car and now the check engine light is on. What could it be? I thought it could be the oil pump but I have no idea
An hour of driving with little or no oil is unfortunately enough to severly damage an engine, and it sounds like what's occurred here.
If there has been a problem with the oil filter seal or the drain plug has been left loose etc. OR by mistake the oil has been drained and not replaced..engine failure can be the result. It does happen.
Firstly don't drive the vehicle any further, and report the incident to the shop that did the job immediately. Have a good mechanic diagnose what the problem is and the likely cause. Also have him record video evidence of the issue. And get a price on repair costs.
If, which is what it sounds like, this is down to negligence on the garages part, you'll need to inform them of what has happened, and what you are intending to do about it. If they are a proper garage and not just a tyre/oil change shop they may offer to repair the vehicle for you. However I'm not sure I'd want a place that can't do an oil change properly stripping/rebuilding an engine. So an independent specialist technician/shop would likely be a better option.
Problems can occur with oil changes especially if they're done by inexperienced guys or garages that offer things like.. ten minute oil changes etc, as they're always rushing, which is not good.
A common issue with filter changes is that when removed the old filter seal sticks to the engine casing, then when the new filter and seal are fitted, two seals end up being attached were there should only be one. This ends up in a massive oil leak do to seal failure under pressure, or the filter itself is actually unable to seal properly in the first place resulting in mass oil loss. If not caught almost immediately, engine damage is normally the result.