I had a similar experience with them (SG). You can check your order status on their site and use the link to your tracking number.
In my case they didn't ship it for several days. Ordered 8/20, and it didn't show up at USPS until 8/23 (two days after they claimed to have shipped it), then started its journey to me. I think this has something to do with their combined 'FEDEX, SMARTPOST' thing.
You will notice that they don't give you the complete USPS tracking number (mine was missing the first 2 digits) so you can't see how it is progressing. Plug their number into USPS and it comes back not found. Only after the package finally arrived and I used the complete number could I see the actual timing of things.
My missing digits were 92, which might be common to their shipping locations, so try appending them on the tracking number you see at SG, and stick that into USPS as see what happens.