I've claimed many players knowing full well that if I get the claim, I'll have to put them back on waivers to get them down in AAA. Sometimes somebody else's AAAA roster depth is better than your AAAA roster depth, so you put the claim in hoping to use them as your injury replacements, not so much b/c you think they'll shore up your ML roster as its currently constructed.
As far as the 1st part, sometimes you check a message, think to check in on it later, then forget about it. Unless I claim a really useful player in the revokable waiver period, I don't stress too much about trading for them. I like to replay to all messages, just good will, but know I let things slip thru the cracks. There is 0 reason in this case to hold it against an owner, it may only cost you (what if they put a player on his back 9 signed to a bad deal at the revokable trade deadline, but don't actually put revokable waivers on him, so that when you claim him, he you automatically get his rights and you are stuck with the bad contract? you said you put a claim in all of their players, best to be careful) Just assume no response is the same as "no thank you" and move on.