I agree with the ownership question on the keg. A deposit doesn't make it yours.
I have a story about trying to return a "stolen" keg that is kind of a counter point to our normal positions though. I'm not justifying keeping a keg, just trying to point out that big distributers (at least in Des Moines) don't really seem to want one back.
I found it difficult to return a Sankey keg gifted to me by a neighbor who was moving. It was "too much of a hassle" for him to return the keg for the deposit and thought, as a brewer, I could use it.
Knowing the keg was worth more than his deposit (and not knowing where he actually picked it up from) I reached out to the distributor to see how to return it to them. I left 5 or 6 massages asking for someone to call me back. Weeks went by, but eventually, I happened to reach an actual person at the company, explained the situation and that I wasn't asking for any monetary reimbursement. To say the least, they were not enthused about me bringing it back. The individual finally agreed that I could drop it at their warehouse and gave me directions.
When I showed up, no one knew what I was doing, much less why. After explaining it to 4 different people in the loading area they finally said "sit it in that corner". I felt like I had wasted 2 - 3 hours of my time and gas trying to do right by them and they could not have cared less. I can actually see them having scraped the keg because it was easier than actually putting it back in inventory.
It can be hard to "do the right thing" when the macro-brewery's intermediary (the distributer) doesn't care whether it comes back or not. I have avoided this kind of issues since then by just turning down kegs when they are offered. If someone wants to keep it, it won't be my problem.
Paul