Hello and thank you for entrusting me to assist you. I am very sorry to hear about this situation.
Unfortunately, employees do not have any legally enforceable expectation of privacy with respect to a company-provided phone. The phone is considered company property and as such the employer retains the right to review messages sent and received from it. So, that would not be a violation of any law.
As for your termination, the general rule is that employment in the state of VA is "at will" absent an express agreement to the contrary. At will employment can be terminated for any reason not amounting to discrimination on the basis of a legally protected trait (race, religion, gender, etc.) or retaliation for engaging in certain forms of legally protected conduct (filing a wage claim, taking FMLA leave, etc.). It doesn't matter whether the basis for termination is fair, reasonable or even true.
So, it would not be illegal to terminate an employee based on the false belief--or even the fabricated allegation--that you were seeing visitors on the yard. You can also lawfully be terminated simply because your employer no longer "wants you in the company," even if their reason is completely arbitrary or personal.
So, it is with regret I must tell you that nothing in the facts you have described would suggest you have any legal recourse here. I do wish I could provide better news, but I trust you will appreciate and honest and straight forward answer to your question so that you can move on.
Please do not hesitate to let me know if you have any questions or concerns regarding the above and I will be more than happy to assist you further. If you do not require any further assistance, please be so kind as to provide a positive rating of my service so that I may receive credit for assisting you. Very best wishes moving forward.