Awesome! You sure know how to bust withdrawal! I only have my Casio keyboard right now.
Hopefully I will not humiliate or excommunicate myself by this admission, but I do / will not suffer from 'uke withdrawal specifically. It's more of general music withdrawal. I stave that off by keeping portable instruments around, like the mouth organs I mentioned and fipple flutes (tinwhistles, ocarinas, etc). My
Casio VL-Tone used to accompany me everywhere. I loaned it to a friend who used it on a song that charted locally but I got it back and still have and use it. What a perv.
(I also had a 1/2 size electric guitar I loaned out that got passed around to local school bands and made it to two more songs that charted, MILL VALLEY [heard around the SF Bay Area] and OH HAPPY DAY [which got national play]. I never got that axe back, grr. But I digress.)
The signs of instrument withdrawal: Twitchy fingers for any fingered axe; I sometime jones on ocarina and keyboard. Twitchy lips if one plays wind / brass instruments. Sweaty forehead and fingers -- probably sweaty toes for pedal players. Nervous shakes, finger twitching and snapping, chord forming and flute fingering. Restless humming and subvocalizing. Spontaneous tuneless whistling. An urge to beat rhythms on anything within reach. (We have a bunch of Native American
ollas (large pots) made of thin clay that I play like a tuned percussion band, and I tap pottery and glassworks in stores.) An urge to pick up a piece of paper and play it like a kazoo. All these occur when an instrument is not in my hands.
In the bright future we will all have cybernetic implants and other body transformations. I envisage a VL-Tone-like keyboard embedded in my left arm, my fingers hollowed-out to use as pan-pipes, and a holographic fretboard projected in front of me by ear-mounted lasers. I am ahead of my time.