I don't think your reconfirming text is relevant, since you've got a written supplement to your written contract, so you don't need to worry about whether it will hold up in court. No contracting party needs to re-confirm anything.
Given that the 5 days includes a major holiday and a time when people don't work, I don't think you can expect anyone to respond the way they might otherwise. Your acknowledged forgetfulness also makes me wonder what the deal is here.
Regardless, give the contractor some more time to address this.
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