Frozen beer and head retention.

[Tipsy]

I put a brew in 2 9lt kegs and accidentally froze one.
After defrosting and carbing, it just never held a head right to the very last glass.
The other keg was perfectly normal though.

Has anyone come across this before?
Does anyone have any theories as to why it didn't hold a head?

[barrelboy]

Thinking about this one. Know it happens with a thawed out can. Did it taste the same as the other keg?
Regards bb

[Tipsy]

They tasted the same, and was carbed perfectly but looked shit because the head disappeared instantly.
I'm drinking the second keg and the head lasts to the bottom of the glass.

I'm not worried about it as the bad kegs gone and hopefully I wont freeze any more beer