My phone icon for one sim out of the two has gone missing.

[Shantanu Indoria]

I have a dual sim lumia 640.
On the start /home page .. I usually have one phone icon for my airtel sim and one for my bsnl sim. But now the phone icon for the airtel sim has vanished from both the home screen and the apps list.
How do i restore it?

 

[Rinsun]

Have you done a soft reset ?
This happened with me yesterday with my Windows Calculator app , icon missing from start screen tile and apps list.In storage it says 'unavailable' .Though app is working okay .Soft reset,resizing tile, checking for updates,nothing helped.Tile is blank and app list icon for calculator is still missing.
Phone is dual sim 535 ,region India.
I do not want to go for hard reset for calculator.
Any suggestions ?