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there's two places an on-hold book will show up. if the book is auto-requested, it'll be on your shelf, with an exclamation point in a grey circle instead of the checkbox. if you hover over it, it will say 'on one-hour hold'. WL books that aren't on auto-request for the first person will also show the grey circle, but will have a pending msg (i don't remember the wording), and they will also show on your Wish List Hold tab.
if you're expecting the book to show on the Wish List Hold tab and it's not there (and it's the right ISBN - which you already checked), it was probably on one-hour hold for an auto-request. if it's on your shelf without the checkmark, then i have no ideas.
you've got some good stuff on your shelf!