lost ? as in can't pull back far enough ?

check the mechanism on the top of the g/box so to see if anything has dropped down or catching on the selector weight
 
its hard to explain ,2nd and 4th feels realy light compared to the top gears wend i give the car some welly through the gears it wont go in 2nd and 4th ,then if i press the clutch then keep it there for a lil while then it will go in
 
I've had this, there's a metal bracket that forms part of the linkage where it passes over the gearbox (a large upright piece of metal is near it) and it snaps really easily, pop it down to a garage while its still got 1, 3 and 5, quick and cheap job.