You’re on the right track, but funnily enough you got it switched around!

Research shows that melatonin binding leads to downstream release of adenosine, so if caffeine is blocking its binding action sleep is not on the way!

Here’s the paper I am referencing: www.ncbi.nlm.nih.gov/pmc/articles/PMC4851458/#:~:….

“We find that melatonin promotes sleep downstream of the circadian clock as it is not required to initiate or maintain circadian rhythms. Additionally, we provide evidence that melatonin may induce sleep in part by promoting adenosine signaling, thus potentially linking circadian and homeostatic control of sleep”