Alonso was about to complete his seventh lap when the rear wheel on the right side came off, sending him into the gravel on the final turn at Circuit de Barcelona-Catalunya.
Under F1's Sporting Regulations, engine manufacturers must inform the FIA by May 15 which teams they have an agreement with in place to supply for the following season.
The Australian was the only driver to reach the 100-lap mark - an excellent return for Red Bull considering previous pre-season schedules had been devastated by unreliability with the auto.
"But we have obligations to help formula one, not Red Bull, and it is obvious that we must plan our work".
"I believe that by the end of May there needs to be some clarity as to who is supplying which team - which supplier is supplying which customer team".
"As far as I can tell, this is our deadline".
Ricciardo's best lap was set on the medium compound and was significantly faster than the top time set on the first day of testing past year, per Sky Sports' Jonathan Green.
"It is important to understand that that reliability gives more options for increasing efficiency".
"In such a situation, the ordering of priorities is obvious", he said in Barcelona. "The key message is that the fact of being reliable opens up more options in terms of performance. I don't want to be negative but it is a bit frustrating when you can't do too much".
The partnership between the drinks brand and former world champions is entering its fifth year and had been up for renewal. Hamilton had flown in from Milan in the morning after attending a fashion event with team partner Tommy Hilfiger yesterday evening, but given the conditions he may have preferred to remain in Italy.
"We are financially stable at the moment.and we are not unduly concerned about them leaving", she added.
Pushed on the reasons for the failure, McLaren racing director Eric Boullier said: "The wheelnut issue was just a wheelnut issue, so I'm not going to comment".