Why would idle revs change mid ride?

Was riding home in the rain yesterday and when I got to one of the junctions I noticed my idle revs were up around 2500, significantly higher than its normally set at, think it sits at 1200-1300 mostly. it was still the same a mile down the road and when I stopped at the next junction, but I got home and all was fine again and has been OK today.

Anything obvious to check? is it a sign of something more sinister perhaps? tis the only odd thing the bike has ever done since new (very nearly 3 years old, doesn't sound much but its a workhorse, 22k miles too)

Thanks

Check for split hoses causing an air-leak, and maybe there could be a problem with the throttle position sensor? I dont think that would cause it though. Maybe some sensor fooling the EFI into thinking the engine is colder than it is and enriching the fuel mixture like its on a choke cycle?