Loosing mails by moving them from inbox to "My Computer"

Hi folks, 

my online mailbox from my server became full. So what I wanted to do is move emails worth a year (appr. 11 thousand) to my computer to free up space. I marked them all in the inbox, right clicked and then "move" -> "on my computer". 

now the emails are gone from my IMAP inbox folder, but no where else to be found - especially not in the "my computer" folder. where do they go? this happened already twice to me.