You do not lose skill points or levels after death- It sounds like you had a Cigar equipped at one point which gives +1 to strength, and later unequipped it.
EG: Your actual strength was 5, and you had +1 from the Cigar, totaling 6. So you then bought rank '7' which was actually rank 6. Later you then unequipped the Cigar, perhaps to swap it for a bandana for the cold/heat resist, which dropped your Strength from 7 to 6 which is the actual rank you own.
Similarly, If you had the buff from..I think steroids? it gives a boost to strength.
Both the semi-permanent buff from Cigar and the temporary buff from steroids allow you to buy ranks in skills without actually having the primary stat raised to the right level- but when either is removed, you do lose access to any skill ranks which require the increased primary stat.
EG: If you have 6 str +1 from cigar, you can buy skills which require 7 strength- but if you remove the cigar, you'll lose acce...
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