The Disasters in your examples – losing an oxygen tank, losing a flipper, losing R2D2 – the way you state them there is actually no "disaster" there. These are just matter-of-fact things that happened. They are the same as "someone lost a handkerchief". We have no context that set up the Disaster: the Goal and Conflict. To put it bluntly, you have no disaster you just have a thing that happened.
The Scene-Sequel model is about character motivation, not so much plot points. For it to be a Disaster in the Scene-Sequel model, it needs to be directly related to the character's Goal and Conflict. The Goal is something intimately personal about your character. The Conflict is a dynamic that is interfering with the Goal. The Disaster is how the goal is not achieved, but it get worse.
Here's my goofy example:
Goal: Jon plans to ask Brenda to dance.
Conflict: Larry is headed in Linda's direction too. Larry is going to ask Linda to dance before Jon! Larry gets everything!
Disaster: Jon breaks into a run to get there ahead of Larry, but sends a tray of food all over Brenda. Oh, no! It's a disaster!
So when the scene starts we only know the goal. As the scene progresses we are introduced to the conflict. If Larry got to Brenda and asked her to dance first, there would have been no disaster at all, and Jon simply could have asked later. But because the Goal and the Conflict together directly lead to the Disaster, and the Disaster now makes the Goal impossible, the reader is (theoretically) hooked by our "perfect scene".
Eventually there will be another scene, the Sequel where Jon's Reaction is to beat himself up for being so clumsy, his Dilemma is how to get Brenda to ever speak to him again. Finally his Decision is to let the air out of Larry's tires.
But we don't have to wait for that scene in the parking lot with Jon. Instead our Sequel could be transferred to Brenda. After a tray of food has been dumped on her (the Disaster set up by Jon), Brenda's Reaction is to feel humiliated, and it was just as Larry was going to ask her to dance! Her Dilemma is whether to run to the bathroom crying or yell at that idiot Jon, and her Decision is now very important because it follows the disaster and now everyone is looking at her. This moment will make or break her reputation. She laughs, so convincingly she almost believes it. Everyone sympathizes with Brenda for being such a good sport while Jon is being thrown out.
I agree with Kirk's answer. If we take these methods too literally they stop being inspirational. It's fun to run a story through these filters to see if we can ring any emotional bells, but it should never feel mandatory. If the system isn't resonating, you shouldn't force it. In this case, I believe what you are misunderstanding is that the Disaster is more of a personal disaster. It's a situation that arrises out of the Goal and Conflict. In my scene with Jon and Brenda, any random person could have been hit with the tray of food and Jon would have been seen as a jerk and it still would have been embarrassing for him. But it's a true Disaster because it crushes Jon's Goal.