In Roman Catholicism even a priest they recognize such as one in the SSPX or some other priest cannot absolve without faculties to do so. Whether it has anything to do with my reasoning I do not know.
All I mean if it wasn't clear is that an absolution involves speaking officially in behalf of the Church. I could pronounce the formula but I am not authorized to do so: I cannot speak in the Church's name as though I were ordained by any legitimate authority. But since we don't tie forgiveness of sins to an absolution even in ordinary circumstances an unauthorized absolution need not entail that forgiveness is not received.
These days deacons and laity may substitute the pronouns and what is delivered is basically absolution. Perhaps there is an implied difference between that and an absolution? In any case that formula could be used in a situation like this should there be any scruples on what is allowed since the alternative formula doesn't seem to be restricted.
This may involve other questions too. An illicit baptism is still valid right? And public in that it is publically recognized as an act of God in the church no matter what the circumstances so long as the proper use of the formula and words are intact. (Some may dispute this. I don't think Anglicans defined any of this.) In that case it may not matter if the absolution is authorized though I don't recommended anything illicit. And it isn't prohibited explicitly so if there is no problem on that count there is no problem at all in my opinion.
There is not much to worry about. Sometimes it is helpful to discuss a problem or even sin with a trusted friend, laity or clergy, even outside of a specific rite of confession. If you desire a sure absolution, attend the Eucharistic liturgy afterward where you will surely be absolved.
Of course the post mentioned a lack of access to a traditional parish. In that case you may still be able to find a suitable liturgy of some other denomination in a parish that pronounces a public absolution. This can be a comfort even if you are not comfortable or barred from receiving Holy Communion.
Failing that you may read the scriptures on forgiveness or have a friend declare them to you to your comfort. You may do all of these things if desired.
There is no need to be troubled. In the early church so far as I have learned there was no absolution as we know it today. God's forgiveness does not depend on it, though it is a comfort to hear the priest pronounce it.
In my opinion in direct answer to your question, yes, it would be valid. Do what you think you should. God won't withhold forgiveness over these irrelevant if interesting technicalities. You aren't breaking any rules! Just keep in mind confidentiality issues that might arise with use of a phone.