The journal is a great tool for showing your collection of pets, as whenever you obtain an item it will be marked off on your journal as collected. 

However, once an item is marked as obtained in your journal, even if you trade away that item, it will still show in the journal. The journal marks off every item you've ever had, not every item you currently have.

As an example, you can see in the following screenshots that the user once obtained a Fool Egg as it is shown in their journal, but it is no longer in their inventory.

The journal is simply to collect pet entries as a way to show off what pets you have obtained. If a pet appears in the journal, it does not mean that you still have it. In Support, we will not give back an item just because it shows in your journal, as you may have traded the item away purposefully, and we will conduct a thorough investigation into any missing items reported to us.