We created a custom landing page with a custom form, which we used to collect customer orders stored in a data extension. The possible choices (type: radio button) were 30, 60 or 90. The subscribers were identified via passing values in an email (using CloudPages function). Unfortunately, there was a mistake in Ampscript code regarding third option (90), resulting in only orders for 30 or 60 were stored in the DE, but 90 were not. Is there any way to retrieve subscribers who clicked on the 3rd option from the cloud page? (Sql, or anything)
Unfortunately there is no way to gather this information as it is only present in the submit HTTP headers and after that it disappears once the processing page is closed. Unless you have some sort of pre-existing analytics around these (which it doesn't sound like you do) or you store the raw submit headers somewhere, you are out of luck.
Usually in instances like this, I would do a benefit analysis on if pushing a 'We made a boo boo' email asking them to update again or just eating the mistake and knowing that it will cause issues in the future is a better route for you.
Sorry to be a bearer of bad news!