- I relearned a profession but didn't get back my higher rank recipes
- I had ranks 2 and 3 of some recipes but using the tome didn't restore them
Forgotten Formulas of the Broken Isles are books available from a vendor, that restore recipes learned from Legion quests and no other source, as well as their rank. For Alchemy, the book only unlocks the ability to purchase the recipes again, and not the recipes themselves.
The book will not restore any recipes from other game-content, nor the profession level. These books are not intended to allow quick switching between professions, their purpose is to recover recipes obtained by quests that are not repeatable.