The one that's ridiculously addictive is MDPV, or so they say.
Because you have no idea what the hell it was you were taking (likely some random cathinone), it's hard to really say much about your experience with it.
However, as to why you didn't get addicted:
1) Crap RoA - You're not supposed to smoke pure chemicals in a manner that involves a flame touching them (which includes smoking out of a normal pipe). You're supposed to chase them off foil, or smoke out of a base pipe.
2) Crap RoA - Smoking, even correctly, is not a preferred RoA for any cathinone stimulant (which is likely what you had).
3) Crap drug - Who knows what it is, but it wasn't MDPV, and it wasn't mephedrone - that means it was something that was likely less reinforcing than those two (ie, less addictive). They're putting all kinds of garbage drugs into "bath salts" (now that the semi-good ones are banned).
4) Low use overall - So you weren't binging, and it sounds like you were't taking that much (by typical standards).
5) Stimulants are psychologically addictive, not physically addictive. So the "withdrawal" would entail being tired and craving the drug, rather than physical symptoms.