Here is the thing:
When you submit a proposal (previously known as a "job application"), you're done with that project until you hear back from the client.
You move on, and you continue working on your existing projects or you submit more job proposals.
You don't sit and wait for the client who posted that project to contact you. He may never contact you.
Until you hear from him and start an interview process or get hired to work on the project, you don't worry about jobs you have applied to.
I wouldn't withdraw it. Just leave it. Sometimes it takes a few hours, sometimes days. Sometimes a client contacts you for a different job a few weeks later. These things happen.
Don't waste your time waiting for someone to possibly contact you. Keep applying for what interests you, and keep moving on. Forget about the application once you have sent it. No job is yours until the contract is awarded to you.
I don't withdraw offers on jobs I am really interested in. It has also happened that I have been contacted after a job has been archived or awarded to someone else, and invited to work on different projects in the same field. Which is why I prefer to archive my proposals myself.
The great thing about continually applying is that there are times that you get better offers and you can be picky. Had 2 people contact me after my proposals were there for 2ish months. I'm booked solid with awesome work right now, but 2 months ago I was not busy enough so throwing out proposals at gigs that I was so-so interested in.
2 dudes come back after they spoke with me 2 months ago and disappeared. I said "meh" and let them go.
One was kinda odd that I'm not sure what was going on there. The guy wanted me to drop my rate to $45/hour and asked me to spend 30 hours one week in a training course and he would pay me $300 for it. 30 hours? WAT no. /ignore