Called 3 times (who knows, might still be calling) within 10 minutes. When I pick up, there is silence. Upon calling back, rings once, and then picks up to silence. Boston area code, so I thought it might be someone I know (I live in Boston), but I couldn't find anything online regarding the number.

Called me and left a voice mail about " a job" I had applied to, a woman named "trudy" left the message, yet when I called back, the number did not exist....

yeah, same thing here. I was applying for jobs in the Boston area and got this number calling me. Firstly, this number left two voicemails. No job opportunity will ever call back if you didn't return their first call. Secondly, it never says what the company is, only saying "we're calling about the job you applied for." Didn't call them back, seems too much like a scam.

It's a woman who works for the agency, Professional Staffing Group.  I just called her and her voice message mentioned that she works for PSG.