Chastity and orgasm denial discussion

Lately my mistress hasn’t felt very sexy, so she has agreed that she can hold my key when I put the cage on, and when I think I’ve had enough, she’ll give it back and we can go back to normal. Trying for longer times, and getting comfortable with the cage in the meantime. Tonight it changed a little. I’d been locked for a few hours, I was thinking of taking the cage off, and she decided to go and hang out with some friends. When I got to our room, after she had gone, I discovered the key was gone! I texted her about it, and she responded with, “What key?” Now I’m not sure whether to be turned on, or nervous that I lost the key (the answer is both turned on and nervous). I don’t know when she’ll be back, and I’ve been getting hard when I think of her having taken the key and holding it in her pocket while she’s out with her friend, and softer when I think I might have lost the key. SO much painful agony and frustration! I don’t know yet how to deal with it, but it is exhilarating. Any words of advice or encouragement, or any thoughts as to what Mistress might be doing with my key?