Um....I'm thinking he told you those cylinders were misfiring, not that they had low compression. If the guy actually told you that the computer was telling him that it had low compression, you need to go back there and punch him out.
Also, if the CEL is on, there's a code there to be read, so the guy was wrong in telling you everything was fine. Reset your ECU, and go drive, if the CEL comes back on report back.
Edit: Also, please report back the actual CEL codes that you get, not the description. Sometimes the discription can be lost in translation, much like I think it is here. I'm guessing the codes were P0301 and P0303.