I've used Second Spin a few times and never had a problem. Sometimes when I have ordered from abroad packages get held up for inspection at customs and it can add to the time it takes to deliver. If you pay airmail postage for items from the US it usually takes a week to 10 days but it can be quicker or longer.
I once waited over 2 months for a package from Japan because it was stuck in
customs.
As for tracing it depends on postage methods, if you've insured the package it is possible but uninsured there's little chance of finding it if it's missing.
I wouldn't worry at this stage. Have faith.