The Hammers icon took to social media to thank fans on Sunday afternoon.
Indeed, the former West Ham midfielder was at Upton Park to watch the east London side draw 0-0 with Stoke City.
And Sinclair, now a pundit for the BBC, was delighted with the reception he was given by fans of his old club.
He was simply disappointed West Ham couldn't beat Stoke to mark the occasion!
As for the game itself, it summed up the current Premier League season perfectly. It had excitement - 34 shots in total - but it lacked the quality needed to win the game for either side.
Both goalkeepers were also in good form, of course, and neither the West Ham nor Stoke camps will complain having avoided defeat against capable rivals.
Next up for West Ham are two away trips - to Swansea City and Aston Villa - and both are most definitely winnable games for the Hammers.
There is plenty of hope as far as a good Christmas period is concerned for the east London club.