Get out of the habit of thinking the airlock is anything other than a vent to release excess co2 and you will be much happier. Your beer will ferment whether or not the airlock bubbles. If it's not bubbling it either doesn't need to release any EXCESS co2, or it's getting out from the bung...either way is fine....If co2 is getting out, then nothing is getting in.
The only way to truly know what is going on in your fermenter is with
your hydrometer. Like I said here in my blog, which I encourage you to read,
Think evaluation before action you sure as HELL wouldn't want a doctor to start cutting on you unless he used the proper diagnostic instuments like x-rays first, right? You wouldn't want him to just take a look in your eyes briefly and say "I'm cutting into your chest first thing in the morning." You would want them to use the right
diagnostic tools before the slice and dice, right? You'd cry malpractice, I would hope, if they didn't say they were sending you for an MRI and other things before going in....
The thin is with a lager, you often don't see much airlock activity, since you are (or should be) fermenting in the cold, co2, like any gas contracts in the cold, so it may not NEED to vent off...in the cold it usually just sits heavily on the beer.
Since you are brerwing a LAGER, turn off the heat....the temp range of lager yeasts is, depending on which type can range from the mid 20's to the low 60's...and if you go higher than the range of the yeast, you will produce off flavors. You should be lagering in a fridge, or other cold area.
So turn off the heater and walk away from the beer for a few more days, more than likely everything was and is fine...if not on Sunday you can take a hydrometer reading to confirm it, but until then just relax, yeast is hardier than most folks think it is....
And remember fermentation is not always "dynamic," just because you don't SEE anything happening, doesn't mean that anything's wrong, and also doesn't mean that the yeast are still not working dilligantly away, doing what they've been doing for over 4,000 years..
Bubbling is a superficial sign...I have 9 fermenters, have been breweing for years and my fermenters only bubble 50% of the time...and I've never problem fermentation.
That's why I stress this so much...it is NOT a reliable way to understanding your beer...and people have tossed out batches just because their airlock didn't bubble. It's not a calibrate instrument, it's cheap ass plastic in a rubber grommet or stopper.