The boss was aware the midfielder was wanted by KV Oostende around a week before he completed a move to Belgium on Thursday.
McGeehan spent the second half of last season on loan at Fratton Park from Barnsley.
He scored two goals in 17 appearances as the Blues suffered play-off semi-final defeat at Oxford last month.
While McGeehan didn't quite meet the expectations of some supporters, having been named in the League One Team of the Season at the Tykes the year prior, Jackett was a big admirer of the former Luton man.
The 25-year-old also said he'd be highly interested in a reunion, having fallen well down the pecking order at Oakwell since Gerhard Struber took over as boss in November.
The Blues missed out on McGeehan, though, as he moved to KV Oostende for an undisclosed fee, signing a three-year deal.
However, that was a switch that didn't shock Jackett as he knew McGeehan was keen to move to the continent.
Jackett told The News: ‘I knew of the likelihood or the possibility that he would go out to Belgium.
‘It wasn't a surprise to me when it was announced.
‘Over recent weeks, I thought it was unlikely that we would get him back because he had this offer. I've certainly known about it for a week or so.
‘Cameron feels that, for him, it's a very good opportunity and we do wish him all the best.
‘When it came out I wasn't necessarily surprised because I knew there was interest.’
Jackett's still relatively well stocked in central midfield despite missing out on McGeehan.
Skipper Tom Naylor, Ben Close and Andy Cannon are all capable of operating in the middle of the park.
Meanwhile, Bryn Morris made his return in the League One play-off semi-final defeat to Oxford following a 14-month absence because of an abdomen injury.
Jackett also feels Gareth Evans can feature in the engine room if required.
He added: ‘We have Bryn Morris back fit, Andy Cannon, Ben Close and Tom Naylor.
‘They are the recognised players we've got, while Gareth Evans has played there quite a lot as well.’