[yakko]

This is more of a 'why' than a 'how' question...

I have a 2002 Regal LS and I've neglected my cooling system for awhile. I know, I know, I'm a bad person. I have had a service engine soon light on for awhile which when I took it to the parts store, they hooked up and told me my thermostat was stuck open.
Well I'm going on a trip for Christmas and wanted to finally get that thermostat taken care of and do a quick flush while I'm at it. After all was said and done, I still had a SES light on. I took it to the Zone and they said I had a cooling sensor fault and an O² sensor fault (P1133).
Now I had given the engine plenty of time to heat up, but an hour or so later when I drove on the highway and got up some speed, the SES light went out and has not come back on.
Now I can understand the cooling sensor may of had some gunk on it and that a flush took care of that, but my question is... could that have affected the O² sensor by somehow causing the engine to run cooler than it should of for this long or something like that? I guess it could make sense, but does anyone have a 'professional' answer?
Thanks.