Well, I had no idea they intended a bullpen game, but if Martin's correct, then Roberts did actually improvise and not stick w/ his "bullpen game" script big time, LOL -- I doubt that's really the case of course, but rather, they probably planned on a plan B contingency of needing it to turn into a bullpen game (and it didn't at all).
But yeah, I started paying closer attention to that game during the final inning before young Sheehan left it and watched much of the rest (on and off)... and really, the Dodgers lost that game for a host of reasons far beyond that one decision, which while questionable, isn't remotely what cost them the game.
Also, you have to remember Sheehan's still a rather young arm they called up from AA (w/ not quite that much experience), not AAA, pretty much for emergency start (and possibly more, if it goes extremely well) or the like. AFAIK, they originally had Bobby Miller going, but I guess decided to give him some extra rest... probably for similar reasons they also chose to take it easier on Sheehan... as they are all promising young arms that still need plenty of build-up and seasoning, not to be pushed like weathered veterans (particularly ones who might not stick around quite that long).
In Sheehan's case, 6IP is the most he's ever even gone before this, and only 2x in his 2-plus seasons in the minors -- once this year and once last year. He usually only went 4-5IPs per game down in the minors where he had it much easier than facing MLB opponents (and basically slicing thru minor leaguers like w/ a hot knife on butter, LOL)... again, not even in AAA yet. So he already far exceeded what they expected and gave them the utmost they could realistically hope for... and yet, he clearly wasn't quite as dominant as fans might want to think since he really only K-ed 3 in 6IPs -- he's actually more used to K-ing 3x(!) as many opponents down in the minors.
Remember, w/ a youngster like him, they have to be concerned about more than just getting an extra out or three in this one game... and that's just how the sport has evolved today (w/ concerns about young arms and injuries, etc) probably for the best even if there might be some wrinkles to improve, etc...
Also, the Dodgers have become so successful because of the process they've developed and (largely) stick to. They're not just gonna ditch the process for just a moment in one game that's not even in the postseason (nor in a tight race in late-Sept). Fans should trust their process in general -- and maybe learn to understand it better, if need be...
_Man_
FYI, if you check the underlying numbers for Sheehan's start yesterday, you'd find he was probably quite lucky to shut out the Giants for that long, NVM no-hitting them... and they'd just be pushing his luck some more if they kept him in there -- he almost certainly wouldn't last the whole inning anyway and might only last 1 or 2 more batters... as they probably shouldn't have him exceed 100 pitches. As it was, the Giants were starting to hit his stuff more consistently hard in the 5th and (especially) 6th innings, and he'd be facing the heart of the lineup a 3rd time in the 7th (while he wasn't really missing bats all along either w/ a very low 4.5% whiff rate and not fooling them that much w/ ~19% chase rate).
Probably best to just let him end his start feeling super good about his no-hit, MLB debut performance (and not needlessly risk his health, future, etc)...
_Man_