As long as your ticket has not been marked as Sold yet, you can request to have it removed from the queue. Just head back to the STEP 'sell' page where you added your ticket into the queue. You can find a link there from the email we sent you confirming your ticket has been added to STEP or by going to the event page on Quicket and clicking the STEP link in the event description. Just make sure you're also logged into your Quicket account.
If you've followed the link in your email, you should be taken directly to your STEP ticket status page. If you've followed the STEP link from the event page, click 'I want to SELL tickets'. You should see a page similar to this:
Click 'Remove from queue'. If the status is 'In queue', your tickets will be released back to you immediately. If the status is 'Offered out' then the tickets will be released back to you if the buyer they were offered to does not purchase them in the 24-48 hour time limit they are given. If the buyer they are offered to does purchase the tickets, the status will change to 'Sold' and you will be refunded in the next refund batch.