Thank you, as your suggestion worked for picking up thrown grenades off the ground and I intended to create this behavior. If you want to allow the thrower the ability to catch his/her's own grenade after throwing it in the air or bouncing it off a wall you have to reset the entity property named "m_hOwnerEntity".
PHP Code:
SetEntPropEnt(entity, Prop_Send, "m_hOwnerEntity", -1);