Different elution profiles of carvacrol and thymol
For gas chromatography, boiling point is one of the most important determinants of elution time.  For thin-layer chromtagraphy, that isn't true.  

The comments from @Molx and @Buttonwood on this question expound on this point quite well.

@Molx:


  Thymol has a lower boiling point (232 °C) than Carvacrol (237.7 °C, both from Wikipedia), I'd bet this is the reason because AFAIK the volatility has a more important effect on the separation than the column polarity in gas chromatography.


@Buttonwood:


  ... gas chromatography's separation is more influenced by volatility (related to boiling point) of the constituents of a mixture than their adsorption to the stationary phase. In addition -- as already stated in the original question -- the column deployed in GC was a non-polar one. Except explicitly stated differently, thin layer chromatography more often uses a polar stationary phase (silica, acid/neutral/basic alumina, for example) where different strength of adsorption is important. [...]