You (or someone with access to your account on a synced computer) deleted 25 collections two days ago. Is that what you're referring to?

If so, you can try restoring from one of the last automatic backups. If you find the collections in a backup but you've made other recent changes you don't want to overwrite with Restore to Online Library, you can create duplicate collections for each of the deleted collections, copy items from each collection to its duplicate, and then sync normally. You'll then download all the recent changes you've made since that backup (including the deletions) but keep the new duplicate collections you created.