DOE L clearance investigation process

For the investigation do they do mailed forms to employers and references or do they do in/person phone interviews with them also? What if your supervisor retired from the company, do you track him down at home? I filled out a SF 86, the HR rep said I wouldn’t be seeing national security information if that matters.

I also have a separate question- I am currently a temp employee at a different federal agency and have been here over a year. I filled out a SF 85 and had no personal interview and only had to give 5 years of info and the form didn’t have a lot of the same questions as the SF86. If I get denied clearance or suitability would I also lose the temp job I have now?