That is likely a spring problem, as I doubt the steel holding those keys in place would have back out of it's own accord. Check to see if the spring is in it's proper position with regards to the spring catch. If it's not, try using a crochet hook or a small screwdriver (being VERY careful, of course) to push it back into place. Be careful though, as excess force may bend the spring, and yield it useless. If everything looks okay in there, without a picture of your flute's specific problem, or a better explanation of the issue, all we can do is recommend you visit a tech. I would suggest you do so anyway after your playing test just to be sure your emergency repairs haven't resulted in unforeseen side effects.
It might be the steel. If it is loose [I have had that happen before with my G# key steel before and had to take the flute apart].
So, if it has worked itself loose, merely take a small screwdriver and screw it back in. [The steel looks like a screw in one of the posts that holds up the G key]. Dont tighten it too much, or else it might not work at all, then you would have to loosen it.
It might also be that you need to oil it. I wouldnt recommend doing this on your own if you havent done this before, but in case you are brave and are willing to accept any consequences of doing it wrongly...... here are the instructions....
loosen the steel in the G key [ it looks like a screw in the post that holds up the G key]. Pull the steel out CAREFULLY. place it on a clean hard surface. remove the G key CAREFULLY [It should pull out with care]. take dentured alcohol and clean the steel rod that you pulled out [use a lint free cloth and dentured alcohol], Next take key oil [not cooking oil, not axel grease, not anything else, it MUST be key oil---specifically made for instruments] and apply a few drops to the rod. Place the G key back into it's original place, and re insert the rod. Screw it back into place. Carefully reposition the springs of the key.
Those are instructions for an OFFSET g key flute. If your g key is perfectly in line with the rest of the keys, then these instructions wont work, then you will have to have a tech fix it for you. I do not recommend taking the g key off by yourself though if you havent done this before. Especially if you dont have the proper tools [small screwdriver, key oil etc.].
I would not suggest doing this, because to get at the G keys on an offset, you must take at least the left hand off, if not the right hand as well, and there are plenty of things that can go wrong with that, even seemingly unimportant things like mixing up which screws go where. You also have to be extremely careful when removing parts of a flute that you don't let the screwdriver slip, as this will strip metal off the screw head, which can make future maintainance much more difficult. Scratching the steel can also cause problems. Not to mention that besides using denatured alcohol on the steel itself, you need to clean out the inside of the rod by using a pipe cleaner (or something similar) with some denatured alcohol. Unless you have been trained on how to maintain/repair flutes (and instructions over the internet, even from a knowledgable source like Adam don't count), it's just not a smart idea to screw around with your instrument.
Sounds risky to do on your own especially since you have a flute test tomorrow and you don't want to accidentally ruin your instruemnt.
Is is possible to explain the situation to your teacher and use a classmate's flute for the exam?
You may want to go to a tech anyway and just mention your case. Where I'm at they'll fix things on the spot of an additional fee if it is an emergency.
I had forgotten that you had to take off the left hand keys to get that off.... Sometimes I havent had to, but I completely agree. Unless you have been taught, and know what you are doing, it isnt a good idea to take your instrument apart. And over the internet sources [ no matter how accurate] dont count.
hope it worked out for your test.. and unless it is a spring out of place,
(my guess from what you have described);
take it to a tech for proper repair.
