Do orthodontists keep the mold of the first retainers they ever gave you? I lost my retainer today.

Generally, if a spacer falls out naturally it is because it has created enough space and is no longer being held tightly between the teeth.  The space will usually close up within a few days (definitely in 19 days), but that doesn't mean they won't be able to get the band around...

Hi! Typically when you're late on a bill for a certain period of time, the doctor can deny treatment. Retainers cost about that price wherever you go. So if you cannot continue treatment, then I would definitely buy the retainers, and wear them daily, so your teeth don't shift.  

Hi, Theoretically it is possible to close the gaps. But it depends on your bone level, sinus lining, bite with lower teeth, bone density, etc. So you should get a proper evaluation with an orthodontist to figure out if it's possible in your case, or if it's even recommended.