The 28-year-old Republic of Ireland midfielder thought he had completed a move to the Championship side ahead of the transfer deadline, only to discover the required documentation had not been processed in time.
Lawrence knew nothing about the hitch until yesterday when he was informed by international skipper Robbie Keane, who had seen a television report, and quickly contacted his agent.
Lawrence said: "Robbie Keane came in at dinner and said, 'Have you seen the telly?', and I said, 'No, why? What has gone on now?' He said, 'You had better ring your agent, then'.
"I spoke to my agent and said, 'What's going off?', and he said the deal had not gone through properly, it was a few minutes late or some rubbish. But we had four minutes to go when we sent the fax off, so I don't know what the big deal is."
Lawrence's comments came after he had played his part in the Republic's 3-1 Euro 2012 qualifier victory over Andorra in Dublin last night with the two clubs working to sort out the problem.
He is keeping his fingers crossed that they can reach a fresh agreement which would perhaps see him join Pompey on an emergency loan deal with a view to making the move permanent at a later stage.
Lawrence said: "I don't know whether it will be one of those loans with a view [to a permanent transfer] and I have already signed. These deals are weird how they work, you wouldn't believe it, so we will just have to wait and see what happens when I get back.
"To be fair, because it took me so long to decide and to sort the deal out - it was a big decision for me, moving down there - I left it quite late.
"But there was still plenty of time and we got the fax sent off, so I don't know what has happened."
Lawrence is at a loss to explain why he is surplus to requirements at the Britannia Stadium - "I don't know, you would have to ask [Stoke boss] Tony Pulis that," he said - but is just desperate to play football on a regular basis.
He said: "I just want to play football and if I go back to Stoke, I probably won't, so I want to go down to Portsmouth.
The midfielder at least remains a key figure for Ireland boss Giovanni Trapattoni, who started him in his team's victories over Armenia on Friday and Andorra last night.
Those wins have left the Republic top of Group B on goal difference and three points better off than favourites Russia, who will look to bounce back from their 1-0 home defeat by Slovakia last night when they head to Dublin next month.
Lawrence said "They are under a little bit of pressure now. They have got to come here and get something.
"I am sure they will come out all guns blazing, so we will just have to make sure we play our normal game, like we do against the big teams, and see if we can get something."
Source: Team Talk
Source: Team Talk