I know of no reason the text message would not be upheld as a valid means of communication by which your employer terminated you, assuming there are no other relevant facts to the situation. Make sure to take an authenticated copy of the text to present at the unemployment hearing. There may be other nuances of employment law specific to communications in your state so you should consider consulting with an employment law attorney there.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.