Every Song Previously Downloaded was Deleted During the Last Upgrade

[E-Break]

Wow, Spotify's last version was pretty glitchy.  However, I was camping recently with a few thousand songs downloaded and Spotify upgraded on my iPhone.  Thanks to this ridiculous upgrade, I have to purchase 10 more gigs of cellular bandwidth.  ABSOLUTELY ridiculous.

[jeremygoh]

Hello @E-Break welcome to the spotify community!

I don't seem to face this resyncing problem, perhaps I was connected to online most of the time.. To avoid this problem in future, you can either not update when you need it for critical use (Apple devices will only auto update when you have wifi) or you can make sure the app is in offline mode..

Good luck!

[Peter__]

Where you "offline" for more than 30 days? An update shouldn't do anything to your offline cache.

[Rodrigo]

Did you try to restart your iPhone by holding the home and power buttons until the screen goes dark and the Apple logo appears? This often solves problems related to the app not detecting data correctly.

How much free space did you have on your iPhone before the update?

When your storage is almost filled, iOS starts to frenetically clean the cache of your apps in a desperate attempt to gather more space so apps can continue working and the system works faster. 

Due to the way Flash storage (this is the type of storage most mobile devices, like the iPhone, use) works, the system needs free space to perform better. That's why iOS cleans the stored data from the apps when it's running out of free storage.

If your amount of free storage was low when you updated the app, your iPhone probably deleted the files.