To get to the point, these signs predate the common use of one single item. If you partner carry around their mobile or cell phone like a body part, this is the number one red flag.
There are also other obvious signs such as coming home late, poorly explained reasons for bieng unreachable, bieng irritatble with you for no reason and generally spending less time at home.
If you read the web, you will find a lot of older articles telling you what signs to look out for when it comes to infidelity.
Shifty eyes, unknown perfume or cologne, buying of new clothes or some Sherlock Holmes lie test.
No more looking foolish, dealing with heartache, embarrassment, or humiliation.