You must be so frustrated! It sounds like it could be a stage, getting ready to make a developmental leap of some sort. He wants something, but he hasn't got the cognitive or language skills to understand or express what he wants. If that sounds like what it could be, I'd be inclined to get out a bit more than normal and see if you can't distract him a bit until it falls into place - or maybe he forgets about it. Or maybe more time with other childen - I wouldn't call it playtime or playdate though!
Hope it passes soon.
