I have an incident report entered into the system this Jan. I left the company while this incident report was not adjudicated, probably because the company had never sent a request to have this incident report adjudicated.
Am I supposed to get a LOJ at the time I left the company?
In my limited experience with this (all second and third hand, fortunately) you will not get a letter or anything unless you try to get another cleared job. Then that incident report will jump up and bite you in the 
In the cases I’ve heard of, the individual had to get a whole new investigation to clear up the incident (whatever it was). And there was somebody on here with a similar concern who could not seem to get any info as to what the “incident” was.
My question here is that: If I leave the employer with an incident report filed a while ago, am I supposed to get a LOJ immediately in my DISS account?
I think you’re supposed to get a Loss of Jurisdiction (LOJ) if you leave a cleared job under any circumstances… I’ve known a few people who had not received any official notice of any kind until they got to their new job and that company’s security office tried to pick up their clearance and saw this big 
in their file.
What I do not know is if any of these people checked their DISS (or had their FSO check) before leaving the first employer.
what is the process of handling LOJ or NDM statuses? As you mentioned, you have to submit an updated SF86. Do they usually go through a full investigation or just investigate the particular issue in the incident report?
I’m in a similar situation at the moment. An incident reported in my case and I had to leave my job before it was resolved. Now the eligibility status shows as “No Determination Made”. I just a got a new cleared job offer and the new company will sponsor my clearance. As I was told by the FSO, they will request my eligibility but the incident will pop-up and they will request an updated SF86. The FSO is not sure the rest of the process if they will do a full investigation back to since last reinvestigation date or just investigate this specific incident.
I think you’re past the most difficult step. Most (well, many) only want to deal with someone with a clearance they can pick up and put you to work generating revenue (ie filling out your time sheet). Now it is just a waiting game.
And I bet they will want to do a full investigation.