My wife recently had the oil changed in her 2000 nissan altima and the next day it started making really loud knocking noise. my neighbor said he this car a had a "oil baffel" where the oil fill is located and the guys may have pushed it into the engine causing this noise. Is there an oil baffell on this model and could this have happened.

Most likely not. It can happen if they jammed a rod down there and poked around and did it on purpose.

Most likely you need to check the oil and take it right back to them if it is full or very near full. These places are known for messing up peoples cars after oil changes. I would go by the amount of oil in the car and mileage since the change.
If you only went a few miles say 50 - you should be able to show evidence it was something done or not done by the oil change people. If it is a comparative lot of miles and there are NO LEAKS of any amount much at all you should be able to get something from them if IF -- the oil level is very low or not showing at all.
If you wait 4 hours after driving the car - then
1- go pull the dip stick from the motor and 2
2 without turning the dip stick sideways or upside down
3- check the level and take a video pic if it is lower than 1 quart -
4 - take this to the people who did the oil change and if the level is low - do NOT drive the car without checking to see if the oil change people are stand up people.

Best of it

Riceski