Jack is with you yet. Every tickle, every soft breeze, every time you sense beady eyes on you (not belonging to an earthbound being of course!), that's your Jackie-baby playing and teasing you, watching over you, never ceasing to love you, and waiting patiently until the horizon on which you...
You're not at all crazy and don't ever doubt yr openness to connect with other creatures/planes of existence. Troubling/emotional periods can cause some ppl to become more sensitive (while others become desensitized obv) so I don't doubt your kitty offered a peek into one of his troubling times...