It’s impossible to give an accurate assessment with a picture but based on what you showed, your description of the events and some experience, analytical thinking and process of elimination I think you do have cause for immediate concern. Perhaps you may be able to provide additional information.
It “looks like” either emulsion from contamination or severe aeration/churning. (Can’t really tell)- I would suggest finding a white light and clean paper towel and perform a blotter test and let’s see how the rings look and any moisture separation from the oil.
Do an olfactory test- does it “smell” of glycol or fuel?
I would definitely perform a field crackle test for water
I would also strongly recommend pulling a sample for analysis (and do a full spectrum because if my suspicion is even remotely accurate then you should get a particle count and full spectrum range of metals and chemistry to try to assess the condition of your engine as well)
I would tend to discount rain and environmental being a contributing factor because if your engine was susceptible to this to that extreme you would have this occur with some frequency. (And assuming you have not been fording creeks and sucked in a gallon of free water- if that’s the case, drop your oil pan and check for bass and bream too)
If it were my vehicle I would immediately change the oil with a standard detergent oil/filter and run about 50-100 miles. (Basically just a washdown, nothing more)
I would recommend a complete mechanical evaluation by a competent mechanic checking compression, cooling system pressure and anything else.
I would ignore (ONLY for the moment) that varnish and build up in the oil hole simply because your description of your event with that low mileage strongly suggests there has been a significant event/change that has affected the oil creating premature failure rather than a long term accumulation. If this is an “event” rather than long term breakdown then that accumulation is more likely than not a symptom caused by the event and subsequent chain of events rather than a problem in and of itself.
After I did that washdown and put your normal oil in I would monitor that fresh change daily and see if the problem starts coming back.
We can guess about everything but I always prefer to technically diagnose and deal with the results.