You already picked up the foam earlier didn't you?
This is a well known glitch.
http://www.gamefaqs.com/boards/960508-shadow-complex?search=foam --- Pokemon White FC: Zippy [2923-8937-6607]
#3chaos_belmontPosted 10/17/2011 1:45:14 PM
There might be some way to get in there but the easiest way would probably be to youst restart and NOT pick up any foam upgrades before you get in there. --- I feel like the concepts of good and evil staggers my inner hatred to leak out in it's purest chaotic/destructive form.