maybe somebody compiled one in a lab, who knows. I've never seen it if they did though. since Win7 has a 32-bit version, in theory there would be nothing to stop there being a 32-bit version of 2008R2, except they just don't want to.
you probly downloaded Server 2008 and not Server 2008 R2 as like said above there is no R2 32bit its only 64bit as like Exchange Server 2010 is only 64bit Microsoft trying to push 64bit now, hence why Windows 7 license is the key works on both 32bit and 64bit the user chooses at install, unless there upgrading there vista install.... (ok not many will know the difference) but as theyve made a 64bit os since XP (ok was a few months after launch) and most people now need 4gb ram due to Apps growing in there needs with technology growing and 32bit only effectivly sees between 3 - 3.5Gb ram depending on some factors.... it makes sence to start pushing 64 as like come on how long have we had 64 Bit CPUs ......