Hi
Try Zooming in on the new join. If, after the split the resulting right hand section is visually narrower than the FX ot the X icon, the latter won't be visible. Zooming in using the scroll wheel or the zoom bar bottom right will widen the clip enough for the FX and X to be seen.
Note also that if you have already added a transition to the join and subsequently move the clips apart, the transition will disappear even when you close any gap to rejoin the clips. In this case you will need to add the transition again.
Nat