Are you sure this is the same library card used to place the hold?
Some families share email addresses. Check your other family members' cards.
Has the 2-day (48-hour) period in which you are allowed to pick up the hold already expired?
If you just missed the window, you can always put the item back on hold. Who knows? If no one was on hold after you, it may be available for you to check out still. Just search for it in OverDrive to find out!
For more details on finding holds please visit the link listed below.