Hey there Ghostmaster!
The Shamac Claus NPC used to recover Regice works similarly to the Nikola Boss, where a player can gain another chance to capture their Regice if they lose the chance to catch it via dc, server crash, killing it, rollback etc.
However, if you release your Regice the only way to recover it is via the Restore Pokemon Megathread where an Admin will assist you in recovering it if you have the Pokemon's ID number.
The post in question, has been edited to reflect this.