If the cards are not showing in My Collection it could be because
a) You have set one or more of the filters and nothing matches
b) You have entered some text in the search box and nothing matches
c) You have used the option to hide them
For the first two cases there will be a "pile" of filtered cards on the My Collection page with a label showing how many cards have been filtered out. If so then cancel the filters and clear the search box.
For case c there will be no indication that any cards are missing. If this is so go to the "view" menu (the icon that look like three horizontal lines located near the top right corner) and select to option to show hidden cards. If any show up then unhide them by clicking on their "unhide" button - it looks like an eye. Hiding cards like this may seem strange, it does to me, but some users requested the ability to be able to get rid of any visible indicators that they owned certain cards)