While some steps in the RCIA program take place at the Cathedral, baptism and confirmation at the Easter Vigil, tends to happen in individual parishes if for no other reason that the Easter Vigil is long enough as is without having to baptise / confirm people from over a hundred parishes as I imagine there would be in Detroit. Although it’s both traditional and appropriate for confirmation to take place at the Easter Vigil (along with the others who have been with you in RCIA) there is no strict requirement for this to happen. I have a family who have just moved into my parish, having been part of the RCIA program in their previous parish (which is significantly larger). If I wanted to do so, there’s nothing to stop me baptising and confirming the whole family (mum, dad and kids) this coming Sunday - which would be appropriate given that it;s the Feast of the Baptism of our Lord. As it happens, I think they need more time and going through the full program would be beneficial for them.
That said, as one who was baptised Catholic before straying from the faith you fall into a slightly different position to most. Although as @Vico has noted, Canon Law allows any priest to confirm those who are being admitted into the Church, strictly speaking you never left it. So, unless during your “born again” period you formally joined another community (say by being “re-baptised”) you’re still Catholic and so your priest would need permission from the bishop to confirm you. Admittedly this applies regardless of when it happens - whether at the Easter Vigil of before. One final thing I’d add is that an individual confirmation would usually celebrated in the context of a mass (although it doesn’t have to be) since it’s a sign of your belonging to the community (for both them and for you) and it would of course have to be in a mass in order for you to receive the Eucharist straight after (again, not exactly essential but makes sense to do both together).