Replacement quit in first week

Obligation to them, no obligation to yourself, yes. Their unfortunate predictament is your gain. You had an agreement with them to leave and you held your end of the bargin. They should of had you assist them in the hiring process. This is their mess not yours, and you could profit from it handsomely. Pitch your out sourcing contract to them and see what falls from the tree. You have the power now to negotiate either to remain with increased pay and probably other "perks" or they will except your outsourcing. They need someone now not in two weeks. Ask them how much money will they loose without position filled? Management's only concern is the ability to reduce loss, increase profit. They are looking bad through their poor decision to their higher ups and if they dont rectify it A.S.A.P. they are in a world of hurt. Jump quickly on this opprotunity before they can rectify on their own. I know you feel loyal to your employer, that's admiral of you, but this is business and easy paydays dont come often in life where you have negotiating power. Good luck!

I suspect the company broke faith with you by selecting a replacement. The severence package was a buyout, and showing the new guy around was the only requirement. The primary intent of a severence package is to make it easier for you to find new employment. Work done, case closed, those payments belong to you.

Now the company is in a jam. New issue to deal with, with new terms. First, you can't trust them as shown by your prior dealings so everything needs to be legal and binding. Next, your value in this circumstance is very specific and limited. If they ask for you assistance and offer an amount, make sure it includes a premium for your very specific added value. Make sure you also get compensated for the job search time you are losing.

Key thing, don't be bitter or vindictive. You have a legitimate product to sell them - your expertise on their system. They are in a sellers market here because of their actions. If you can get a deal that you are happy with then take it, but if not just move on.

Athouugh you were "rolled under the bus". Usually what goes around does not come around so quickly. The company is shaken by their cheap alternative not working out.

Keep the severance, it is yours. They agreed to pay you to go away. If they want you back, they must pay again. This being the case, don't gloat, set a fair rate for your services and stick to it. If they are unhappy with the rate you ask, point out that they created the situation, not you.

If brought in on a contract basis,resist the temptation to bring your status to the attention of higher ups. Just make sure that your hourly rate is generous enough to make yourself happy.