Are there any HR/Employment Insurance experts out there that can answer my question?

Until Monday afternoon I worked for a Company Based in Illinois, but was employed through their Michigan location, Insured through their Arkansas BCBS and I reside in Pennsylvania.

I currently have a gap in coverage as i was terminated just days before starting a new job so i am left with a gap in coverage. My company had already paid the premium on the plan to the end of May and I share in the cost 50/50 with the company as a pretax deduction so you would think that They already paid and I already paid for the full month but i was informed that my insurance coverage was terminated at Midnight Monday.

I know this is a real oddity based on 4 states being involved but it seems odd to me that they can terminate a policy mid month after i have contributed to the payment of said policy and they have contributed as well?

I am trying to avoid paying for COBRA as i start my new job next week. I was planning on Resigning from my job anyway.

Can anyone advise if they have any expertise in this area and if what they did is even legal?