Subject to the provisions of this article, the rights of a player's services may be lent to another league of…
Subject to the provisions of this article, the rights of a player’s services may be lent to another league of the club, provided that the following conditions are met, except where otherwise expressly prohibited elsewhere:
a) Regular exceptions were requested and cleared during the playback period and
(b) The player has not played in ten (10) or more NHL games that are cumulative since regular exceptions to him were last cleared and more than thirty (30) days cumulative on an NHL -rosts have not gone since usual exceptions to him were cleared last. -NHL collective agreement
What is said if a player has cleared the exception, as Pirri did on 10/4/18, he can be revoked and play for up to nine matches OR be active more active for up to 29 days without needing again clear exceptions.
Brandon Pirri was recalled to Golden Knights on 1
2/18/18. Before tonight has played in eight matches then recalled. He has been on roster 19 days.
If he played in two matches OR was on active roster for 11 days, he would once again be subject to an exception if the golden knights wanted to send him down to the AHL.
It gives us today. Due to injuries and illness, the royal knights had only 12 active and available on the list of Pirri. Reilly Smith, William Carrier, Erik Haula, and eventually we learned Cody Eakin, were all inaccessible to play in this evening’s game. Thus, without Pirri, Golden Knights only had 11 available forward.
Enter another CBA provision called “Emergency Recall”.
(ii) Recalled from a minor league club of emergency recall and plays in ten (10) NHL games (cumulative) in emergency recall. For the sake of clarity, games played during regular recall should not be counted among the ten (10) NHL games in this subsection (ii). – NHL collective agreement
Since Golden Knights only had 11 ahead without Pirri, they were officially in an emergency. Then they returned Pirri to AHL, stopped the non-emergency clock at eight matches, recalled him during the emergency memory, and now has a brand new clock.
Thus, Pirri played tonight as a game at his emergency department. As long as Eakin, Smith, Carrier and Haula ALL are still inaccessible to play, Pirri continues to play on the emergency clock. At the moment one of the four is available, Golden Knights must immediately return Pirri to AHL, stopping the emergency clock. If they want to revoke him again, they will restart the non-emergency clock sitting for eight matches and 19 days.
Emergency clock – 1 game, 1 day
Emergency clock – 8 games, 19 days  So there you have it. That’s why it happened, and why George McPhee is smarter than you, and I, and probably the rest of the NHL (at least a few hours until I figured it out.)