What if I can only provide strong circumstancial evidence of retaliation, but no concrete "proof"?

For the year and a half I have worked for my company, I have been an "All-Star Model Employee". I have never received even a verbal warning. I have consistently gone above and beyond for my company. I filed a complaint with OSHA. I cannot prove that the person (my now-ex-girlfriend who works for the company) informed my supervisors that I was planning to file. The day OSHA contacted my employer, I was written up for a bogus charge. The next day the ex-girlfriend claimed that I made threats against the company to her on the phone. I was suspended that day, and fired at the end over the phone without so much as being included in an investigation. In addition, during a private one-on-one meeting with my Area Supervisor just after announcing my suspension, he made the comment (along the lines of), "I'm going to be very busy today since /someone/ (he used noticeable inflection) made a complaint to OSHA, so we'll be pretty tied up". He also encouraged me to resign, saying that it would be "the responsible thing to do", and at the end of the day claims to have filed a police report against me on the basis that "just in case I decide to threaten our clients"! I felt very intimidated at that point. I have no direct "proof" that they're retaliating, but considering that their claims are only substantiated from a 3rd party whom I have been in a relationship with (which ended badly), they have no actual evidence in my firing. Do I even have a chance of proving I was retaliated against?