Welcome to the STD forum. Oral herpes isn't considered an STD, but it's close enough. You also could ask on the herpes expert forum.
Assuming you're in the US, there's a 50:50 chance you have HSV-1 yourself, since half of all adults do. Most of them have no symptoms, so lack of past cold sores doesn't mean you don't have it. If you do, you're immune to a new infection and there is no risk at all. Second, with your friend's oral herpes virtually completely healed, the odds are good that transmissible virus was no longer present. That said, I cannot say there was no risk. To the specific questions:
1) All things considered, probably less than 1 chance in several hundred that you caught HSV-1.
2) Saliva can contain HSV-1 in people with active infections. However, simple contact with saliva may not be sufficient for transmission. In general the virus has to be "massaged" into the exposed tissues. That's why initial genital herpes usually shows up at the points of maximum friction during sex, e.g. penis in men and vaginal opening and labia minor in women, and uncommonly the labia major, scrotum, groin, etc.
3) Probably minimally contagious by the time a scab has fallen off.
4) Oral herpes probably is fairly often transmitted by "inanimate objects", like pipes, tooth brushes, etc. Not as commonly as by kissing, but it happens.
5) HSV dies immediately with drying and is unlikely to survive in the environment more than a few minutes. Herpes is not transmitted by contact with dry objects in the environment.
6) If the pipe stem was heated to anything over about 50 C (say 120 F -- too hot to touch) and then allowed to cool, it probably was effectively sterilized. Any less then that and probably not.
Bottom line: The chance you were infected is very low. You might already have it; this could be determined by a blood test, if you care to go to the trouble. If I were in your situation, I wouldn't get tested and I wouldn't be worried.
Regards-- HHH, MD
Thank you. I realized immediately after I posted my question that I said it was in the "post-scab healing stage," but I might have gotten scabbing and crusting confused. She had the yellowish crust, which fell off a few days ago, but there was still a red spot that looked like it was healing, which may be a scab (I'm really not sure, I didn't touch it). Does this change the likelihood of transmission? Sorry if my language was imprecise.
Once healing is well underway, the virus usually is gone. Maybe this raises the risk a little higher than I suggested initially, but not enough to worry about.