All the end crystal disappeared from obsidian pillars

entered the end for the first time and jumped off because I had no stuff with me. The second time I went in, I was shooting the crystals, thinking I had trash aim, I pillared up to see there were no crystal on top of the obsidian pillars. Every pillar were empty of end crystals. Seeing that the cages havnt yet been destroyed, I assumed it just disappeared. This was also a vanilla server with a few plugins.