I would prune it back and wait. Thyme is a tough plant but it's possible it got winter killed especially in wet clay. It might have been better to not give it the protection. Leaves and compost will tend to keep it wet all winter.

If it looks dead, it probably is. My thymes retain their leaves all winter - no matter purple they look!

I have had poor luck overwintering all but the standard, common thyme (Thymus vulgaris). I think the common thyme is the toughest and hardiest of the thymes.

I too have clay soil but I make sure that plants like thyme are in the best draining locations I have. Sitting in water is sure death for these plants especially during the winter season.

FataMorgana

"If it looks dead, it probably is. My thymes retain their leaves all winter"

Thank you. There may be one tiny twig on the plant that still has a couple leaves. Other than that, zip. I'll cut it back; I got nothing to loose at this point. And let it sit there a while more while looking for a replacement. [What could go wrong? Maybe end up with 2 tymes instead of one?]

Certainly give it a chance if you think there is life still in it! Good luck!! :)

FataMorgana