Sadly, I've not had great success in recovering APFS volumes. The file system is very different from the older HFS+ file system that is recoverable! But that was quite awhile ago! Things are getting better give this a try! [https://www.prosofteng.com/mac-data-recovery|ProSoft - Data Rescue 6] using the free version.
At this point your actions will make the difference in the data recovery. You need to create an external bootable drive and the size of this drive needs to be bigger than your internal SSD drives used data space. The reason is the recovery process will move the files to this drive and as you wiped the volume this might require a a larger drive.
***So what happened?***? I'm suspecting you used an older version of Disk Utility which doesn't know how to access the newer APFS volumes. I've seen that a few times now as people use an older Sierra boot drive to boot up the system or used the recovery partition OS which is Sierra or older. Even High Sierra has issues! As Apple altered the APFS file system in Mojave so the older High Sierra Disk Utility won't work properly either!
***By why did I loose access to my system if the drive was OK??*** Simply put the PRAM battery died! If you remember it sits on the back side of the logic board you'll need to pick up a fresh BR2032 battery!