I assume you use the menu very fast? If so then you should notice this behavior for all grenade types.
Take a look below. I'm using this code to check for grenades on players death accordingly so take it just as an idea.
PHP Code:
new iAmmo = cs_get_user_bpammo(id, CSW_HEGRENADE)
// = 1 pullpin (animation is played if you press +attack)
// = 2 thrown (animation is played if you release +attack)
// get_user_weapon (active weapon) and user_has_weapon (including non-active weapons) will return true because the grenade is still in your hand.
new iAnimation = pev(id, pev_weaponanim)
if (get_user_weapon(id) == CSW_HEGRENADE && (iAnimation == 1 || iAnimation == 2) iAmmo--
if (iAmmo > 0) client_print(0, print_chat, "Player has still a grenade")
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