Mem,
Sorry this happened to you -- it is extremely rare, but unfortunately, not unknown.
Registrars are given certain connections (the oft mentioned "Pool 3") to the registry that can be used for acquiring deleting domains. However, using these connections does not affect the ability of a registrar (or its resellers) to register domains manually using the standard connections. Because of this, a reseller or end-user may be able to manually register a dropping domain through a registrar that SnapNames is partnered with for that same purpose. It almost never occurs but is theoretically possible, as was shown in this instance. Please accept my apologies.
Also, once a name is registered SnapNames blocks the back-order position on that name until the whois record updates to reflect the new owner. It will appear that the name was immediately back-ordered after acquisition, but in fact its just being made unavailable as a mechanism for avoiding the situation that domaingator and tonyk2000 describe.
Kjel Holmberg