Another hypothetical

[Larry1953]

Let's say there are runners on first and second with one out and a 3-2 count on the batter. R1 thinks there are 2 outs or he thought he saw the steal sign that R2 did not get. He is off with the pitch which the catcher thinks is strike three but is called ball four. The catcher throws through to second where the runner overslides the bag and is tagged out R2 hangs close to second until he is sure ball four is called and trots to third. Meanwhile F2 throws to third where the tag is placed before R2 reaches the bag. Defense contends R2 is out because he was no longer "forced" to the next base once R1 was called out at second. What is the correct ruling? I think R2 is safe at third and R1 is out.