I subscribed to iCloud before erasing my phone and lost much of my music in the process

I subscribed to iCloud before erasing my iphone and synced my iPad with cloud, only to learn that many previously purchased songs went missing in the process.

The missing songs are not displayed in iTunes Store/ Purchase, thus I assume they're lost forever. But if anyone knows of a trick or a method I can use to get them back, well I would love to know about it and I thank you in advance for your time.