I've hidden Cydia and Poof! With the Poof! Cydia tweak. Now I cannot open either one of both of them.
Is there any way to undo this? I've tried respringing and rebooting but that does not place them back.
If you have version 0.9.3997 or greater of MobileSubstrate…
This enables Safe Mode, disabling all MobileSubstrate tweaks temporarily, allowing you to uninstall the tweak that's causing problems. If you still want the tweak, you can reinstall it, deleting the preference file for the tweak in question to reset it.
To exit Safe Mode, you can respring/reboot your device, or press Exit Safe Mode in the status bar, then press Restart.
If you have a tethered jailbreak, you'll need to hold volume up whilst pressing 'Just Boot' and continue holding even after the Apple logo since Substrate won't load immediately.
I think it will be fine if you restore your iPhone again and Cydia download again on your iPhone