How to detect user uninstalled iOS App? I need push serious notification. I don't wanna lose it -

i know apple won't let know user uninstalled app.

my problem
have old legacy sms system send alert short message end user. of these messages serious. bottleneck gsm module has limitation when send hundreds sms users simultaneously. delay inevitable.

thus, build new alert system send push notification users, if installed app. after register phone number, sms alert switched new alert system.

problem old school users prefer sms rather push notification. download app, , register phone number. then, found phone doesn't have 3g data plan. deleted app without un-register phone number.

my new system has no idea deleted app without unregister phone number. serious alert messages still keep sending nonexistent app 1 phones.

my question
there smart idea or mechanism can detect user have deleted app?

apns has feedback service apple reports device token no longer active on users device. required apple check tokens feedback service , stop sending pushes devices.

you can use same information automatically move user sms. tie device token phone number in database. if token active, send pushes it. if reported feedback service in-active, remove records , use users phone number sms again.

just remember device token can become active again, @ point, registered through same mechanism first time. re-save user , use push again.