The phrase "admittedly missing" is correct and usable in written English.
It can be used when acknowledging a lack or absence of something in a candid manner.
Example: "The report is admittedly missing some crucial data that we need for our analysis."
Alternatives: "clearly lacking" or "undeniably absent".
(They did, admittedly, miss smoke alarms off the list. But perhaps ads telling you how refreshing a certain branded drink might be at the moment your house is burning might be a step too far, even for an overreaching ad giant).
To talk this way is, admittedly, to miss the point of "Nameless forest".
The personal, psychological and physical sacrifices required to escape Jigsaw's traps are missing, admittedly (unless you count losing control of your bladder in front of friends/family/strangers), as is the personal development that they were designed to provoke (unless you count the post-coaster rush of endorphins).
Admittedly one thing missing is the product.
Admittedly, all these missing data undermine the validity of our results.
Picking five bowlers would admittedly mean young James Taylor missing out and I was really impressed with him in this game.
The width, movement and threat on show against an admittedly poor Bulgaria was missing at Wembley and Wales keeper Wayne Hennessey was barely troubled apart from Young's goal.
While they admittedly appear to be missing other large pieces of the smart car puzzle, including manufacturing, autonomous systems and retail and service, you simply cannot bet against them with three-ish years to go and Tim Cook seemingly ready to play Santa Claus.
Also, it was admittedly hard to miss the differences between the problems my students faced and the problems I obsessed over at home.
Secondly, I had to hand in each day's segment by midday (though admittedly I did miss this slightly once or twice), so I didn't have much time to reread and alter what I'd done.
Admittedly, I would miss them.
