Bognor ensured their Conference south survival and immediately dedicated the achievement to long-serving boss Jack Pearce.
A Luke Nightingale wonder goal ensured Rocks the point they needed in a hard-fought 1-1 draw at struggling Thurrock.
Coach Darin Killpartrick said: "We have done it against the odds with a restricted budget but we are so pleased to stay up. We wanted to do it for Jack. He has done so much for this club. We owe him such a debt."
Pearce, who has been in charge at Bognor for 37 years, wanted to take a step back until the end of the season to re-charge his batteries after a roller-coaster campaign.
Killpartrick feels maintaining their Conference south status will have provided Pearce with a huge boost.
He said: "Jack had a big smile on his face afterwards."
The hosts took the lead through a Lee Flynn free-kick on 15 minutes but former Portsmouth striker Nightingale secured the point with a shot on the turn from 20 yards six minutes after the re-start.
Bognor: Stoner, Ruby, Chamberlain, Rowland, Wallis-Taylor, Howell, Birmingham (Balfe), Beck, Hudson (Watson), Nightingale, Johnson (Budd). Subs not used: Hunwick, Farrell.
Boss Steven King insisted Lewes would be stronger next term after their play-off hopes were finally extinguished.
Rooks scored a 2-0 victory against struggling Hayes at the Dripping Pan thanks to a strike and a header from Jean-Michel Sigere on 31 and 71 minutes.
But fifth-placed Bishop's Stortford's deadlock with Bedford wiped out any chances of a late bid for the top five.
King said: "The amount of draws we have had killed us. We will be the stronger for all the experiences with most of the squad staying plus four or five additions for next season."
Lewes: Williams, Hamilton (Drury), McKie (Wormull inj, Cade), Simpemba, Robinson, Legge, Greatwich, Holloway, O'Connor, Sigere, Kennett. Subs not used: Booth, Farrell.
Eastbourne Borough boss Garry Wilson remained defiant after his side's 14-match unbeaten run was ended with a 3-1 defeat at Sutton.
Borough were 2-0 down at half-time in their fourth game in eight days after Warren McBean and Bashiru Alimi netted for the hosts within a three-minute spell. Allan Tait pulled one back from close range on 51 minutes and Borough then bombarded the home rearguard before John Scarborough completed the scoreline towards the end.
Wilson said: "We are still on the edges of the play-offs and have five games to go. We are still in the mix."
Borough: Hook, Baker, Lovett, Harding, Wilde, Austin, Pullan (Douglas), Armstrong, Atkin (McArthur), Ramsay, Tait. Subs not used: Agutter, Lightwood, Murray.
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