Adult disability payment application missing

Hi all. I searched the forum before posting but only found one post and it didn’t have a resolution. I submitted my ADP application (Scottish version of PIP) within my deadline this Tuesday. I didn’t receive any confirmation email, so today (Thursday) I went on the web chat to check it went through.

I was told it did not, there was no trace of it and I’d have to start again. Aside from being a massive pain given the effort it took, it would also obviously mean losing any back payment if successful - backdated to today instead of early August. I raised to the adviser and said I did download the completed application when I submitted. They then said I can either post them a copy with a covering letter, or call and do a dummy application by phone and then upload the previous application as supporting evidence and it will apparently be backdated properly.

Does anyone have any experience of this?

I’m struggling to work out which route is the better one to get the ball rolling quickly and make sure the original start date is observed.