Is it normal to be suspicious of a really interesting finding but in an obscure journal and/or by authors from unknown universities
I am concerned by your choice of words:


"Obscure": one person's obscure may be another person's core community.
"Low IF": IF is very dependent on both community and "trendiness."  A lot of very good work is published in low IF venues because they are the appropriate place to publish the result.
"Unknown ... and unexpected": again, not unusual at all for something interesting to come out of an unexpected place.


All of these words, to me, point to lazy "popularity-contest" thinking in evaluating the context of a work.  Instead, I think that you should use more scientifically meaningful heuristics, such as:


Does the investigator have a history of solid work, into which this result fits?
Does the venue have a clear, well-defined focus and community, and does it have reputable management?
Is the work well-suited for the venue?


If a work doesn't pass these filters, then I think you should be highly suspicious and not bother digging more deeply.  If it does, however, then you should be just as skeptical as you should be for work coming out of a high-prestige laboratory in a leading institution---and no more.