The Sheffield Wednesday striker’s loan spell expired earlier this week and he returned to Hillsborough after scoring four goals in 13 appearances.
Lavery tweeted his thanks yesterday afternoon but Pompey have not given up hope of tying up a new deal.
The striker could yet seal his return before Saturday’s noon deadline but the stumbling block appears to be at the Sheffield Wednesday end as Pompey press for an agreement.
So Cook has had to make plans to cope without him.
Cook said: ‘We all want to keep Lavs.
‘He is a really good player and a good lad.
‘But it’s a case of “watch this space”.
‘I can’t answer whether he will be signed before the weekend – I would only be guessing.
‘It’s something we are speaking about at the moment but if we can’t do it, then we can’t do it.
‘The pleasing thing for us is Caolan wasn’t with us last week at Ipswich and it didn’t seem to affect us.
‘We’ve got good players who can come in, so the show goes on.’
Meanwhile, James Dunne has had his contract cancelled by mutual consent and has joined Cambridge United.
The combative midfielder was one of the club’s most consistent performers in the early part of last season after signing from Stevenage in summer 2014.
He made 39 appearances and scored one goal.
But he was clearly not part of Cook’s plans and his first-team opportunities were restricted to just one substitute appearance this term before he was loaned to Dagenham & Redbridge.
– STEVE WILSON