Depleted Bognor brought in Chichester City forward Kaleem Haitham for his debut - but slipped to their first defeat in five games on their long trip to Brightlingsea Regent.
With Dan Smith and Brad Lethbridge on Pompey duty and Jimmy Wild on holiday, the Rocks turned to their neighbours and dual-signed Hatiham, who has been impressing in the Oaklands Park club's charge to the top of the SCFL premier division.
Haitham played just over an hour of the Bostik premier clash - which kicked off late because some of the Bognor contingent had a delayed journey to Essex - but he couldn't help save Jack Pearce and Robbie Blake's team from a 3-0 defeat.
It was their first loss since December 15 and followed a run of three wins and a draw over the Christmas/new year period.
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Regent took the lead in the 25th minute through Harvey Hodd and doubled it five minutes after the break through Jordan Barnett, moments after Dan Lincoln had made a superb save.
To compound a night to forget for the visitors Billy Hunt added a very late third.
There was a second appearance off the bench by centre-half Corey Heath as he continues his comeback from an ankle injury, while youngster Josh McCormick was given another start.
Bognor will hope for better when they go on Saturday to Burgess Hill - who themselves had the perfect warm-up for the Bostik premier Sussex derby by knocking Pagham out of the Sussex Senior Cup.
The Hillians won 3-0 at Nyetimber Lane, where they had trailed 2-0 in the original game when floodlight failure caused the match to be abandoned.
In division one of the SCFL, Selsey won 2-0 at Southwick. Remi Coates and Lindon Miller were on target for Daren Pearce's team.