1
The magician made the rabbit disappear.
Sign 'MAGICIAN', 'RABBIT', then use the sign for 'disappear' with a sudden, sharp downward motion. Emphasizing the speed of the sign helps convey the suddenness of the magical vanishing act to your audience.
2
My keys disappeared from the table.
Sign 'TABLE', 'MY', 'KEYS', and then 'disappear'. Pair this with a confused facial expression, furrowing your eyebrows and slightly shrugging your shoulders to show that you have no idea where your keys went.
3
The sun disappeared behind the clouds.
Sign 'SUN', 'CLOUDS', then 'disappear'. Instead of a fast drop, you can move your dominant hand down a bit more smoothly and slowly to mimic the sun gradually fading from view behind the weather.