I've never experienced the fuel injection warning myself, but it's quite common on the Vel Satis and other Renaults, going by my years of trawling other Renault forums online, plus speaking with other Renault owners.
It's sometimes to do with a blocked EGR valve, so maybe it just needs cleaning. Sometimes it's a filter that's clogged, or sometimes it's something more serious. It could just be a mystery though, which might rear its head every so often, but not cause any long term issues.
Member 'DMH52 Vel Satis' on this Vel Satis forum experiences the fuel injection warning fault every few weeks in his Vel Satis, which is a 3.0 diesel. Exactly the same happens to him as happened to you i.e. he got the warning, the car went into limp-home mode with a restricted top speed of 50 mph, and he only got out of limp-home mode by turning the engine off and back on again. He tells me that often the fuel injection warning fault appears when he floors the car hard, after it's not been used for a while (cold engine and all that). But sometimes it happens when he's trundling along nicely on a motorway, comes to overtake, them bam, warning comes up again, even though the engine's been running fine for an hour or so.
And yesterday, R9UKE on here reported via Twitter (we're @renaultvelsatis on there – twitter.com/renaultvelsatis) that a relative of his' 3.0 also threw up the fuel injection warning fault for the first time. But apparently his relative was doing considerably fast speeds.
I know it doesn't really help, but 'DMH52 Vel Satis' definitely has this quite often, and his local Renault garage told him they couldn't find a fault in particular, despite plugging in Dialogys and CAN CLIP (the official Renault software and hardware tools via ODBC).
Maybe another owner can throw some light. I wonder if Rosic with his 2.2 has ever had the fuel injection warning light?
Keep us posted. Do you have a garage nearby you can take it to, just in case?