The non-league club claimed last month they had agreed a deal to sell him to the Black Cats late on deadline day.
However, the move fell through as the EFL failed to rubber stamp the deal following difficulties that arose during his medical.
Lovatt, once a trialist at Leeds United, will train with the Foxes this week alongside teammate Jamie Fielding.
Portsmouth have agreed a new contract with midfielder Ben Close.
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The 22-year-old put pen to paper on a deal which will keep him at Fratton Park until the summer of 2021, with an option for an additional 12 months.
Close’s previous deal expired in the summer of 2020 but boss Kenny Jackett moved to extend his stay with a string of impressive performances this season.
Since his debut in September 2014, the boyhood Pompey fan has appeared 111 times - netting eight times.
Fleetwood Town manager Joey Barton will take training this morning, despite allegedly assaulting Barnsley's Daniel Stendel on Saturday.
It is believed South Yorkshire Police have still not contacted Town after reports yesterday suggested Stendel needed emergency dental treatment.
Stendel was captured on camera returning to work on Monday and reports in the national media claim he has spoken to the police to assist with their enquiries.
The FA say they will be reviewing the referee’s report but will only get involved once the police investigation ends.
Peterborough United chairman Darragh MacAnthony has revealed the club have completed two pre-contract signings ahead of the summer.
MacAnthony was speaking to Posh's YouTube channel, discussing plans for next season in detail. He said: "We’ve already signed two players on pre-contracts.
“We are allowed to talk to players now who are coming out of contract at the end of the season and Darren will then deliver a presentation of what his plans are."
Meanwhile, MacAnthony confirmed Joe Ward has been offered a new contract while stating the club is not interested in a George Boyd return.
In League Two, Yeovil Town loanee Alex Pattison has been told by his parent club Middlesbrough that he will be released at the end of the season.
The 21-year-old has been on the books at Boro since the age of nine and was loaned out to the Glovers this term without making a senior appearance on Teesside.
"Would just like to thank everyone at Middlesbrough for the last 15 years I've spent there and some of the memories and people I've met.
"Time to move onto to a new challenge next season, but for now the focus is the last big push these last four games at Yeovil."
Pattison isn't the only Boro youngster to be released with Kieran Charlton, Nathan Guru and Dan Ward also being let go.
League One play-off dates
1st Leg - Saturday May 11, 7.45pm KO
2nd Leg - Thursday 16th May, 7.45pm KO
1st Leg - Sunday May 12, 12.15pm KO
2nd Leg - Friday May 17, 7.45pm KO
Sunday May 26, 3pm KO - Wembley
League Two play-off dates
1st Leg - Thursday May 9, 7.45pm KO
2nd Leg - Sunday, May 12, 6pm KO
1st Leg - Friday, May 10, 7.45pm KO
2nd Leg - Monday, May 13, 7.45pm KO
Saturday, May 25, 3pm KO - Wembley