The arguement of the idea that Jessie would be afraid of Tuco wouldnt mean to much considering Tuco was a well known figure in the underground, Jessie is an active user. Users dont generally stick to just 1 source as not all meth is the same. Some better than others, which Tuco or his camp could easily have been 1 source of many in the show. Jessie could have easily learned about Tuco from Skinny Pete, also considering Pete and Tuco were locked up together cementing Tuco's reputation.  Tuco is a Salamanca  which most dealers would know is a cartel linked name.  The argument could have been... Jessie went to score and got his car jacked instead, not reporting it knowing tuco is family to cartel.  Jessie being green could have easily made Jane suspicious but it would have been a logical argument and destroying the narrative that Walt would be linked to Jessie or Tuco's property in the desert.   Walter buying weed wouldnt any further link would have also been plausible since Walt was actively dealing with cancer and chemo.    Personally I think it would have been much harder for Jane to figure it all out unless he actually broke Jessie, Skylar or Walt