Not all plans require spousal consent... it is up to the document the employer has for the plan... technically it is not "your money", but his for retirement.. Spousal rights come into play, should something happen to your husband, or is there is a divorce. If it is not an ERISA plan, then joint and survivor annuity, may not apply.
So in short... No- you would not have had to approve or sign off on this loan.Some plans do require it, and it would have had to been notarized, but the majority DO NOT require your consent.

Your husband had that money set aside under his social security number as an asset for his retirement. These 401k products are exclusionary as marital benefits until they are withdrawn from the 401k account, preferably after retirement.

Your husband secured a loan with his credit against these funds, using them as collateral. As long as he didn't use your income to get the loan, no signature on your part was required.

Yes, the spouse has rights when retirement kicks in, or when money is withdrawn from the 401K, and usually has to sign along with the retiree. A loan is a little different, however. as properly describe above.