If you did not receive a citation or some other form of written notice of an arrest (with a date to appear in court), you could receive a notice in the mail that charges have been filed and notifying you to appear on a date certain. The DA might also decide to file charges and seek an arrest warrant, in which case you might be noticed and you might not even know that charges have been filed. You might consider hiring an attorney to monitor this situation and find out if the case is being...
You can be arrested for a DUI on certain circumstantial evidence of driving even if the arresting officer didn't actually see you driving. These rough facts would seem to fit the bill. However, the case may be defensible and you should consult with a criminal defense attorney asap to explore all your options. Remember, you only have 10 days from your arrest to request a DMV hearing or you will lose your license regardless of any defenses you may have.
If the charge are filed and a warrant is issued within the statute of limitations period, the statute is tolled. You may have some other defenses, however. You should contact an attorney in Washington State to discuss your options
Yes, an attorney can help. The prosecutor will probably know about your previous offense if it resulted in a conviction, and of this case results in a filing it will be reflected on your record. You're a young guy; I hope you have learned your lesson this time.
Your attorney should be assisting you with this. Interestingly, there were some very recent cases on just this issue that should be reviewed before deciding to seek appellate review. I'm sure your attorney has looked into this and will advise you accordingly.