We havent but LEOs try to make a big deal over shit like this just to justify their position and overly large budgets.Not all mind you but quite a number of departments.I would bet the grenade was inert and if it was live and dangerous it would have most likely gone off some years ago.
I remember from a diagram somewhere that the detonator is lead azide. Wiki says that stays stable in storage.
Then again, the TNT filler doesn’t last forever:
“TNT is prone to exudation of dinitrotoluenes and other isomers of trinitrotoluene. Even small quantities of such impurities can cause such effect. The effect shows especially in projectiles containing TNT and stored at higher temperatures, e.g. during summer. Exudation of impurities leads to formation of pores and cracks (which in turn cause increased shock sensitivity). Migration of the exudated liquid into the fuze screw thread can form fire channels, increasing the risk of accidental detonations; fuze malfunction can result from the liquids migrating into its mechanism.”