What is a "transition" as stated in an IFR flight plan.  I followed the plan under ATC until "resume own navigation".  I continued on following fix points, headings, altitudes as previously assigned but was no longer "in the system".  I landed (illegally) without any further input from ATC.  Was my failure to follow "the MSN transition" cause for being "dumped"?

If you were cleared for the MSN transition, then you need to follow that route.  Or, you can ask Approach Control for vectors to the ILS for Runway xxx.