I suggest you let your executive committee and strata manager know of this situation in writing immediately and do your best to contact the new owner and suggest they call off, or at the least stall, the sale if possible (cooling off periods may be in force, contracts may not have been exchanged, settlement may not have taken place etc.) Complain to the head of the real estate agency concerned etc. in writing. Tell everyone. Make as big a noise as you can. It'll sort itself out.