Do you have the original contract info? sounds like it was a 6 month gig? Sept to March?
Sounds like you are not an employee of the Pharm Company. You do not get a pay check from them, but rather thru the agency. They pay you and handle the withholding taxes etc. If you were an independent contractor you’d get a 1099 from the Pharm firm. The “at will” state of NJ is not relevant as you are not a full time employee of the Pharm firm.
I had in my Mgt days let contract employees I got thru an agency go on short notice from time to time. It was absolutely a Budget decision. Occasionally it would be a job performance issue, that appears to not be the case here. You being on vacation is not relevant.
When I had budget issues we always let the contract employees go first and not lay off the full time employees unless it got desperate. Full Time employees I had to pay severance pay and unemployment etc.
If your funding came from a Project budget, which could be likely in this case, either the budget for the Project ran out or the Project got cancelled.
The actual work you did may not be relevant as you were tied to the funding of a project budget.
Being a contractor makes a lot of employment law not apply.