The seven-time world champion was beaten in Spa by team-mate George Russell, with the Mercedes pair finishing ahead of Oscar Piastri, who rounded off the top three.
However, on what should have been a perfect day for the Brackley-based team at the last race before the summer break, their celebrations were halted following a shock post-race development.
It was a devastating blow for the 26-year-old, who had delivered a magnificent performance on a one-stop strategy to keep his rivals at bay.
Russell hailed after devastating blow
The team error robbed Russell of his third career victory - and second of the season after winning in Austria - and handed Hamilton the victory instead.
Speaking on the Formula for Success Podcast, former McLaren driver Coulthard sympathised with Russell given what transpired, but was quick to praise his 'winner's mentality', which should stand him in good stead going forward.
“It was a cracking race - it was a really good race except if you’re George Russell, so let’s address that first of all," said the Scot.
“He seems that he drove the decision to go for the one-stop from the cockpit, so that’s a winner’s mentality.
"Not just following the instructions of the team which would have almost certainly put him behind Lewis Hamilton who drove faultlessly, it has to be said."